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譯文題目: 動力轉(zhuǎn)向系統(tǒng)的演變
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年 02月 18日
The Evolution of Power Steering
By Randy Wilson
Brief introduction for power steering
Power steering helps drivers steer vehicles by augmenting steering effort of the steering wheel. Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only modest effort regardless of conditions. Power steering helps considerably when a vehicle is stopped or moving slowly. Also, power steering provides some feedback of forces acting on the front wheels to give an ongoing sense of how the wheels are interacting with the road; this is typically called "rοad feel".
Representative power steering systems for cars augment steering effort via an actuator, a hydraulic cylinder, which is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure still permits the vehicle to be steered using manual effort alone.
In other power steering systems, electric motors provide the assistance instead of hydraulic systems. As with hydraulic types, power to the actuator is controlled by the rest of the power-steering system.
Some construction vehicles have a two-part frame with a rugged hinge in the middle; this hinge allows the front and rear axles to become non-parallel to steer the vehicle. Opposing hydraulic cylinders move the halves of the frame relative to each other to steer.
History about power steering
The first power steering system on an automobile was apparently installed in 1876 by a man with the surname of Fitts. Little else is known about him. The next power steering system was put on a Columbia 5-ton truck in 1903.
Robert E. Twyford, a resident of Pittsburgh, Pennsylvania, USA, included a mechanical power steering mechanism as part of his patent issued on April 3, 1900 for the first four wheel drive system.
Francis W. Davis, an engineer of the truck division of Pierce Arrow began exploring how steering could be made easier, and in 1926 invented and demonstrated the first practical power steering system. Davis moved to General Motors and refined the hydraulic-assisted power steering system, but the automaker calculated it would be too expensive to produce. Davis then signed up with Bendix, a parts manufacturer for automakers. Military needs during World War II for easier steering on heavy vehicles boosted the need for power assistance on armored cars and tank-recovery vehicles for the British and American armies.
Chrysler Corporation introduced the first commercially available passenger car power steering system on the 1951 Chrysler Imperial under the name "Hydraguide". The Chrysler system was based on some of Davis' expired patents. General Motors introduced the 1952 Cadillac with a power steering system using the work Davis had done for the company almost twenty years earlier.
Charles F. Hammond, an American, born in Detroit, filed several patents for improvements of power steering with the Canadian Intellectual Property Office in 1958.
Most new vehicles now have power steering, owing to the trends toward front wheel drive, greater vehicle mass, and wider tires, which all increase the required steering effort. Heavier vehicles as common in some countries would be extremely difficult to maneuver at low speeds, while vehicles of lighter weight may not need power assisted steering at all.
These systems have come a long way but still require regular maintenance.
Steering assist and control is one of the many systems we have seen continually change and evolve over the years. All of the OEMs have invested millions of dollars into the advancement of steering controls.
We, as technicians, have seen simple manual gear boxes replaced by hydraulic ones. We've seen gear boxes, or sectors, give way to rack and pinion assemblies that operate with more advanced hydraulics. And now, electronic steering systems are not uncommon.
Not only do we have to continually learn new material as these systems come to market, but we have to maintain our knowledge of past and present systems. Whatever the age of the system or how advanced it might seem, regular inspection and maintenance is the common factor they all share and need to work properly.
Pieces, Parts and Components at a Glance
With steering being such a safety related aspect, and with such a high demand placed on this part of a vehicle, inspection of the steering and suspension system on every vehicle should be a priority.
An important thing to look at first, of course, is the hardware, it takes very little time to do a good, thorough inspection of steering components when you have a customer's vehicle in the air. Don't be afraid to grab a tire at the top and bottom and give it a good flexing in and out to make sure a hub and bearing assembly doesn't have excessive play. Bearings carry a lot of weight and pressure and should be checked on a regular basis.
Almost no play at all should be felt in a sealed hub and bearing assembly. Tapered bearings should be cleaned, lubricated and properly adjusted for preload to prevent overheating and bearing failure.
Upper and lower ball joints are a must for inspection. Many are sealed and have no accessible grease fittings for service. These take quit a beating. Not only are they the pivot point for the front steering knuckles, but they also endure a ton of lateral force. Always inspect the boots for splitting or damage and make sure to check for play in both upper and lower joints. To accurately test ball joints for wear, be sure to follow the specific procedure outlined in your service information system for the vehicle you are working on. Some vehicles use visual indicators; some require specific lifting procedures to "unload" the joints for inspection.
Tie rod ends, both inner and outer, should be checked in much the same way. Inspect the boots and check for excessive play or wear. Most vehicles can be checked by grabbing each wheel at the 9 and 3 o'clock positions, and attempting to rock the wheel back and forth. If any noticeable movement is felt, use one hand to grab the outer tie rod assembly to see if it is the cause of the play. If not, grabbing the tie rod shaft will allow you to feel any movement that may exist in the inner tie rod joint.
Steering systems that use a drag link or center link set up with idler and pitman arms should be inspected just like the tie rod ends. Wear in these components can have some serious safety concerns and cause excessive tire wear. Always make sure that any of these parts having fitting for service are properly lubricated. Do not overfill the grease boots, as this will lead to rupture and premature failure of the components.
If the system is hydraulic, always inspect for leaks. Whether it's a rack and pinion or worm gear and sector type unit, both operate under high pressures. Pressures can exceed 1,000 psi in many systems, and a leak can deplete the system of fluid rapidly. Make sure hoses and lines are routed properly and away from exhaust components or moving parts.
Make sure to look at compression fitting, as well as connection to power steering pumps and gears, for leaks. Always inspect pumps for leaks at case seams and shaft seals and make sure to maintain the correct level of fluid in the reservoir.
If the pump is belt driven, inspect the belt for wear or damage. Listen for unusual noise from the pumps as compared to a like vehicle. A noisy pump is a definite indication of a problem whether it's a failure or something like air being induced into the system that can lead to a failure. Air being pulled into a system can cause an excessive whine and can lead to premature pump failure if not addressed.
Of course the driver's feedback for the entire system is the steering wheel. Always inspect the steering shaft from the gear back up to the column no matter what the design. Most systems entail a series of universal joints, slip yokes, crush shafts or some type of intermediate steering shaft that leaves the gear and connects to the column. This is the last thing you want to fail on a curvy stretch of highway at 65 mph. Most of these are manufacturer specific and require very little in the area of maintenance, except for inspection, but are a vital part of the steering system. The column itself should be checked for freedom of rotation to make sure there is no loose play in the column bearings.
Electric power steering systems will usually have an integral column and an electric assist design. These systems are usually replaced as an assembly and will not likely have serviceable components in the column except for the electric components themselves. With that being said, they should still be inspected as any other column design.
Service is Still the Answer
As with any other system on the vehicle, we know power steering needs service as well. There are many serviceable hard parts in any steering system, but with good routine maintenance, most components will last for a long time. Our customers have to be educated on the need for regular service to a system like power steering.
Pivot points and fittings should always be lubricated or greased at regular service intervals. Pinch points or steering stops should be lubricated as well. And of course let's not forget about that fluid in the hydraulic systems. These fluids are under very high pressures and operate at extremely high temperatures. Even though the fluids are designed for this kind of environment, viscosity and thermal breakdown can and will occur. The fluid can begin to burn and break down, and as components in the system degrade where the fluid travels, contaminants begin to build up in the fluid.
Should these fluids be serviced like any other fluid in the vehicle? Absolutely. It takes only a few minutes to pull a sample of fluid from a system and inspect it for burning and contamination. If they're present, it's probably a good time to flush, clean and refill the system.
There are many good systems on the market for flushing and cleaning power steering systems. Some systems will connect right into the vehicle power steering system, while others simply extract and reintroduce fluid or cleaners right through the fluid reservoir.
There are also some pretty good conditioning products that come along with these systems as well. With the advent of high quality synthetic power steering fluids, you can offer your customer an even better choice when it comes to fluids operating under extreme conditions. With these products we can offer a good service that can save customers a lot of money and give them peace of mind.
動力轉(zhuǎn)向系統(tǒng)的演變
蘭迪﹒威爾森
動力轉(zhuǎn)向系統(tǒng)簡介
動力轉(zhuǎn)向系統(tǒng)幫助司機通過增大方向盤轉(zhuǎn)向力度來操縱汽車。液壓或電動執(zhí)行器往轉(zhuǎn)向機構(gòu)增加控制的能量,因此不管任何條件下,駕駛員只需要提供適度的力就可以了。當(dāng)車輛需要停止或緩慢移動時,動力轉(zhuǎn)向系統(tǒng)對此有相當(dāng)大的幫助。此外,動力轉(zhuǎn)向系統(tǒng)提供一些力反饋作用在前輪上,得到車輪與路面如何相互作用的持續(xù)感,這是通常被稱為“路感”。
代表汽車的動力轉(zhuǎn)向系統(tǒng)通過一個執(zhí)行器---液壓缸來增大汽車轉(zhuǎn)向力,這是一個伺服系統(tǒng)的一部分。這些系統(tǒng)在轉(zhuǎn)向盤和轉(zhuǎn)向輪聯(lián)動之間有一個直接的機械連接來操縱車輪。這意味著,動力轉(zhuǎn)向系統(tǒng)故障時,仍然允許車輛轉(zhuǎn)向單獨使用手動力來操縱車輛。
在其他的動力轉(zhuǎn)向系統(tǒng)中,電動馬達(dá)提供的幫助代替了液壓系統(tǒng)提供的幫助。對于液壓類型,致動器的動力是被動力轉(zhuǎn)向系統(tǒng)的其余部分控制的。
有些施工的車輛配有一個由兩部分組成的框架,在框架中間連接有堅固的鉸鏈,這鉸鏈允許前軸和后軸成為非平行軸來使車輛轉(zhuǎn)向。對置的液壓缸移動相對于對方的框架的一半來轉(zhuǎn)向。
關(guān)于動力轉(zhuǎn)向系統(tǒng)的歷史
汽車的第一動力轉(zhuǎn)向系統(tǒng)顯然是在1876年由一個姓菲茨的人安裝在汽車上的。很少有人知道他。下一個動力轉(zhuǎn)向系統(tǒng)是在1903年被安裝在一輛哥倫比亞5噸的卡車上。
羅伯特·E.特福德,美國賓夕法尼亞州匹茲堡的一個居民,在1900年4月3日第一次發(fā)行四輪驅(qū)動系統(tǒng)作為其專利的一部分,其中包括機械動力轉(zhuǎn)向機構(gòu)。
弗蘭西斯·戴維斯一名皮爾斯·阿諾的卡車部門的工程師,開始探索如何轉(zhuǎn)向可以變得更容易,并在1926發(fā)明和展示了第一個實用的動力轉(zhuǎn)向系統(tǒng)。戴維斯之后到了通用汽車公司工作,然后完善了液壓助力轉(zhuǎn)向系統(tǒng),但通用汽車公司計算出若生產(chǎn)液壓轉(zhuǎn)向助力系統(tǒng)將太過昂貴。戴維斯隨后與為汽車制造商提供零部件的本迪克斯公司簽約。在第二次世界大戰(zhàn)期間,更容易轉(zhuǎn)向的重型車輛的軍事需求帶動了英國和美國的軍隊的配有轉(zhuǎn)向助力的裝甲車和坦克救援車需求。
克萊斯勒汽車公司推出了第一款商用轎車動力轉(zhuǎn)向系統(tǒng),在1951年克萊斯勒帝國為它取名為“液壓轉(zhuǎn)向裝置”??巳R斯勒公司的系統(tǒng)是基于一些戴維斯的一些過期的專利。通用汽車公司在1952年推出了一款凱迪拉克,這款凱迪拉克的動力轉(zhuǎn)向系統(tǒng)用的是大約二十年前戴維斯就已經(jīng)為公司做過的工作。
查爾斯·F·哈蒙德,一個出生在底特律的美國人,在1958年向加拿大知識產(chǎn)權(quán)局申請多項關(guān)于動力轉(zhuǎn)向系統(tǒng)的改進(jìn)的專利。
現(xiàn)在大部分新的汽車都有動力轉(zhuǎn)向系統(tǒng),由于前輪驅(qū)動的車輛,有更大的質(zhì)量,和更寬的輪胎,這些都增加了所需轉(zhuǎn)向力的需求。在一些國家,常見的較重車輛低速行駛將是非常困難的,但重量更輕的機動車可能根本就不需要助力轉(zhuǎn)向。
這些系統(tǒng)已經(jīng)走過了漫長的道路,但仍需要定期維護
在過去的一些年中,轉(zhuǎn)向助力與控制是我們看過的許多不斷改變和發(fā)展的系統(tǒng)之一。所有的原始設(shè)備制造商已經(jīng)投入了數(shù)百萬美元在轉(zhuǎn)向控制的提升上。
作為技術(shù)人員的我們,已經(jīng)看到了簡單手動齒輪箱被液壓式的所取代。我們已經(jīng)看到了齒輪齒扇式的轉(zhuǎn)向裝置讓位給更先進(jìn)的液壓齒輪齒條式組件?,F(xiàn)在,電子轉(zhuǎn)向系統(tǒng)并不少見。
因為這些系統(tǒng)進(jìn)入市場,我們不僅必須不斷地學(xué)習(xí)新的材料,我們還必須保持我們的過去的和現(xiàn)在的系統(tǒng)知識。無論是什么年代的系統(tǒng)或是看起來多么先進(jìn)的系統(tǒng),定期檢查和維護是他們正常工作的共同因素。
部件及零配件的概況檢查
隨著轉(zhuǎn)向成為影響相關(guān)方面安全性的重要因素,并以如此高的需求配置在汽車部件上,所以對每輛車的轉(zhuǎn)向和懸掛系統(tǒng)的檢查應(yīng)該優(yōu)先。
首先要做的一個重要的事當(dāng)然先檢查它的硬件。當(dāng)你有一個顧客的汽車架在臺架上時,它需要花很少的時間來對轉(zhuǎn)向部件做一個良好的、徹底的檢查。別害怕抓住一個輪胎頂部和底部,然后給它一個良好的里外彎曲,以確保輪轂軸承總成沒有過度發(fā)揮。軸承承受大量的重量和壓力所以需要進(jìn)行定期檢查。
長時間的工作應(yīng)該在一個密封的輪轂和軸承總成中被感受到。圓錐軸承應(yīng)被清潔,潤滑和適當(dāng)調(diào)整預(yù)緊力來防止軸承過熱和軸承失效。
上下球接頭是一個必須要進(jìn)行檢查的一個項目。許多上下球關(guān)節(jié)是密封的,沒有裝置可供添加潤滑油。這些零件應(yīng)避免敲擊。它們不僅是前轉(zhuǎn)向節(jié)的樞軸點,同時他們也承受一噸的側(cè)向力。請務(wù)必檢查轉(zhuǎn)向節(jié)的裂紋和損壞并確保檢查上、下關(guān)節(jié)是否正常工作。為了準(zhǔn)確測試球關(guān)節(jié)的磨損情況,請務(wù)必遵循你正在使用的汽車中的服務(wù)信息系統(tǒng)里所提到的特定程序。一些車輛使用可視化指標(biāo);還有一些汽車則需要特殊的解除程序來“卸載”關(guān)節(jié)進(jìn)行檢查。
拉桿端部,包括內(nèi)側(cè)和外側(cè)的,都應(yīng)以相同的方式來進(jìn)行檢查。檢查部件看其是否過大和磨損。大多數(shù)車輛可以通過抓住每個車輪在9點鐘和3點鐘位置,,并嘗試搖滾車輪來回檢查。如果任何明顯的運動感覺,用一只手抓住外拉桿總成,看它是否是引起彎曲的原因。如果不是,抓住拉桿軸會讓你感覺到可能存在于內(nèi)橫拉桿接頭里的任何運動。
轉(zhuǎn)向系統(tǒng)使用拉桿連接或與惰輪和連桿臂設(shè)立的中心連接轉(zhuǎn)向系統(tǒng)應(yīng)該像拉桿球頭總成那樣被檢查。在這些部件中的磨損會有一些嚴(yán)重的安全問題和引起過度的輪胎磨損。始終確保有配件服務(wù)的任何部件都能得到正確的潤滑。不要給部件裝太多的油脂,因為這將會導(dǎo)致部件的破裂和過早故的失效。
如果系統(tǒng)是液壓的,要經(jīng)常檢查是否有泄漏。無論是齒輪齒條式還是蝸輪蝸桿式的,兩者都是需要在高壓下進(jìn)行工作。在許多系統(tǒng)里壓力都可以超過1000psi,一個油泄漏會使液壓系統(tǒng)迅速的癱瘓。確保軟管和管路布置得當(dāng),應(yīng)該遠(yuǎn)離排氣部件或運動部件。
在壓縮配件,以及動力轉(zhuǎn)向泵和齒輪連接,一定要看看是否有泄漏。在有接縫和軸密封的情況下一定要經(jīng)常檢查泵是否有泄漏,確保油罐中液壓油位在正常高度。
如果泵是依靠皮帶驅(qū)動的,要檢查皮帶磨損或損壞情況。與類似的車輛相比,聽泵有無異常噪聲。嘈雜的泵是存在一個問題的明確指示,不管這問題本身就是一個錯誤還是像一些空氣一樣的東西被誘導(dǎo)到系統(tǒng)中而導(dǎo)致的故障。被吸進(jìn)系統(tǒng)中的空氣如果不加以解決的話,可能會引起很大噪音和導(dǎo)致泵過早出現(xiàn)故障。
當(dāng)然,司機的反饋對整個系統(tǒng)是方向盤。不管是什么樣的設(shè)計一定要經(jīng)常檢查轉(zhuǎn)向軸,從齒輪直至轉(zhuǎn)向柱。大多數(shù)系統(tǒng)需要一系列的萬向節(jié),滑軛,擠壓軸或某種類型的中間轉(zhuǎn)向軸,使齒輪連接成一列。這是你需要做的最后一件事來防止車子以65英里每小時在彎道上行駛時發(fā)生跑偏。其中大部分的部件都是特定的制造商生產(chǎn)的,除了檢查外,很少需要進(jìn)行維修,但這是轉(zhuǎn)向系統(tǒng)一個至關(guān)重要的部分。軸承本身的自由旋轉(zhuǎn)應(yīng)該被檢查以確保在軸承中沒有松動存在。
電動助力轉(zhuǎn)向系統(tǒng)通常會有一個完整的柱和電動助力設(shè)計。這些系統(tǒng)通常是作為一個組件更換,在這些部件中除了電子部件外,不會有需要維修的部件。也就是說,他們?nèi)匀粦?yīng)該像任何其他的部件一樣被檢查。
服務(wù)仍然是答案
與汽車上的其他任何一個系統(tǒng)一樣,我們知道動力轉(zhuǎn)向也需要服務(wù)。在許多轉(zhuǎn)向系統(tǒng)中都有許多維修堅硬的部分,但具有良好的日常維護,大多數(shù)組件將持續(xù)很長時間。我們的客戶受到教育對于像動力轉(zhuǎn)向系統(tǒng)一樣的系統(tǒng)定期服務(wù)是有必要性。
樞軸點和配件在定期間隔維修時應(yīng)進(jìn)行潤滑或上油。夾點或轉(zhuǎn)向站應(yīng)潤滑良好。當(dāng)然,我們不要忘記,在液壓系統(tǒng)中的流體。這些液體處于高壓下,而且是在非常高的溫度下工作的。雖然油是專門在此種環(huán)境中設(shè)計的,但粘度和熱破壞還是會發(fā)生。流體可以開始燃燒和分解,并作為系統(tǒng)組成部分在流體行進(jìn)的系統(tǒng)中降解,然后污染物開始在流體中產(chǎn)生。
這些流體有像汽車?yán)锲渌牧黧w那樣的功用么?絕對有。它只需幾分鐘就可以從系統(tǒng)中抽取一個樣品液體,然后檢查它的燃燒和污染。如果它們存在,那么這可能是一個很好的時間來沖洗,清潔和重新加注系統(tǒng)。
在市場上有很多好的系統(tǒng)來沖洗和清洗動力轉(zhuǎn)向系統(tǒng)。一些系統(tǒng)將正確連接到汽車的動力轉(zhuǎn)向系統(tǒng),而另一些只是通過流體儲層簡單地提取和恢復(fù)流體及清潔劑。
也有一些不錯的冷卻裝置是隨著這些系統(tǒng)而來的。隨著高質(zhì)量合成動力轉(zhuǎn)向液的到來,當(dāng)流體在極端條件下工作時,你可以為你的客戶一個更好的選擇。通過這些產(chǎn)品,我們可以提供好的服務(wù),可以為客戶節(jié)省很多錢,讓他們安心。
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