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譯文題目： The Evolution of Power Steering
動力轉向系統(tǒng)的演變
學生姓名： 徐澤洲 學 號： 1204104048
?！ I(yè)： 車輛工程
所在學院： 機電工程學院
指導教師： 凌秀軍
職 稱： 講師
2016年 2月 22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.
動力轉向系統(tǒng)的演變
蘭迪﹒威爾森
動力轉向系統(tǒng)的簡單介紹
動力轉向幫助司機通過補充方向盤轉向力度來操縱汽車。液壓或電動執(zhí)行器向轉向機構增加控制的能量，因此不管在什么條件下，駕駛員只需要提供適度的力。當車輛停止或緩慢移動，動力轉向的幫助很大。另外，動力轉向系統(tǒng)提供了一些作用在前輪上力的反饋，得到車輪與路面如何相互作用的持續(xù)感，這通常稱為“路感”。
代表汽車的動力轉向系統(tǒng)通過一個致動器---液壓缸來增大轉向力，這液壓缸是伺服系統(tǒng)的一部分。這些系統(tǒng)在方向盤和聯(lián)動之間有一個直接的機械連接來操縱車輪。這意味著，動力轉向系統(tǒng)發(fā)生故障時，仍然允許車輛轉向時單獨使用手動力來操作。
在其他的動力轉向系統(tǒng)中，不是液壓系統(tǒng)提供的幫助，而是電動馬達提供的幫助。至于液壓類型，致動器的動力是被動力轉向系統(tǒng)的其余部分控制的。
有些施工車輛配有一個由兩部分組成的框架，在框架中間配有堅固的鉸鏈，該鉸鏈允許前軸和后軸成為非平行軸來使車輛轉向。對置的液壓缸移動相對于彼此的框架半部來轉向。
有關動力轉向系統(tǒng)的歷史
汽車上的第一個動力轉向系統(tǒng)是在1876年由一個姓菲茨的人安裝在汽車上的。很少有其他人知道他。接下來的動力轉向系統(tǒng)是在1903年被安裝在一個哥倫比亞5噸的卡車上。
羅伯特·E.特懷福德，美國賓夕法尼亞州匹茲堡的居民，1900年4月3日第一次發(fā)行四輪驅動系統(tǒng)的專利，其中包括機械動力轉向機構。
弗朗西斯·戴維斯，一名皮爾斯·阿諾的卡車部門工程師。他開始探索如何可以更容易轉向，于1926年發(fā)明，并展示了第一個實用的動力轉向系統(tǒng)。戴維斯之后到通用汽車公司工作， 完善了液壓助力轉向系統(tǒng)。但汽車制造商計算出若生產(chǎn)液壓轉向助力系統(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向助力的裝甲車和坦克救援車需求。
克萊斯勒公司推出的第一款商用轎車的動力轉向系統(tǒng)，在1951年克萊斯勒帝國為它取名為“液壓轉向裝置”?？巳R斯勒系統(tǒng)是基于戴維斯的一些過期的專利。通用汽車公司在1952年推出一款凱迪拉克，這款凱迪拉克的動力轉向系統(tǒng)是用的是近二十年前戴維斯就就已經(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，于1958年向加拿大知識產(chǎn)權局申請多項關于動力轉向系統(tǒng)的改進的專利。
現(xiàn)在大多數(shù)新的汽車都有動力轉向系統(tǒng)，由于前輪驅動，更大的汽車重量，更寬的輪胎，這些都增加了所需轉向力的趨勢。在一些國家，常見的較重車輛在低速行駛將是非常困難的，而重量更輕的機動車可能根本就不需要助力轉向。
這些系統(tǒng)已經(jīng)走過了漫長的道路，但仍需要定期的維護。
在過去的一些年中，轉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。所有的原始設備制造商已經(jīng)投入了數(shù)百萬美元在轉向控制的提升上。
作為技術人員的我們，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)看到齒輪齒扇式的轉向裝置讓位給更先進的液壓齒輪齒條式組件?，F(xiàn)在，電子轉向系統(tǒng)也并不少見。
因為這些系統(tǒng)進入市場，我們不僅必須不斷地學習新的材料，我們還必須保持我們的過去的和現(xiàn)在的系統(tǒng)知識。不管系統(tǒng)是什么年代或它可能看起來有多么先進，定期的檢查和維護是它們正常工作共享的共同因素。
部件及零配件的概況檢查。
隨著轉向成為影響相關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，所以應該優(yōu)先檢查每一輛車的轉向和懸架系統(tǒng)。
首先要做重要的事當然先檢查它的硬件。當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向部件做一個良好的、徹底的檢查。不要害怕抓住輪胎的頂部和底部，然后給輪胎一個良好的里外彎曲，來確保轂和軸承總成沒有過度的發(fā)揮。軸承承受大量的重量和壓力，應該進行定期檢查。
長時間的工作應該在一個密封的輪轂和軸承總成中被感受到。錐形軸承應該被清潔，潤滑，適當?shù)卣{整預緊力，以防止軸承過熱和軸承故障。
上下球關節(jié)是必須要進行檢查的一個項目。許多上下球關節(jié)是密封的，沒有裝置可供添加潤滑油，這些零件應避免敲擊。它們不僅是前轉向節(jié)的樞軸點，它們還承受大量的側向力。請務必檢查轉向節(jié)的裂紋和損壞并確保檢查是否正常工作在上、下關節(jié)。為準確測試球關節(jié)的磨損情況，請務必遵循你正在使用的汽車中的服務信息系統(tǒng)里所提到的特定程序。有些汽車使用可視化指標，還有一些汽車則需要特殊的解除程序來“卸載”關節(jié)進行檢查。
拉桿端部，包括內側和外側的，都應該以幾乎相同的方式來進行檢查。檢查看其是否過大和磨損。大多數(shù)的車輛都可以通過抓住每個車輪在9點鐘和3點鐘位置，并嘗試著搖晃車輪來回檢查。如果有任何顯著的運動感覺，用一只手抓住外橫拉桿總成，看它是否是引起彎曲的原因。如果沒有，抓住拉桿軸將讓你感受到任何可能存在于內拉桿接頭里的任何運動。
使用拉桿連接或與惰輪和連桿臂設立的中心連接轉向系統(tǒng)應該像拉桿球頭總成那樣被檢查。在這些組件中的磨損，可以有一些嚴重的安全問題和造成輪胎磨損過度。始終確保有配件服務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，因為這將會導致部件的破裂和過早故障。
如果是液壓系統(tǒng)，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行操作。在許多系統(tǒng)里壓力都可以超過1000psi，油泄漏會使液壓系統(tǒng)迅速的癱瘓。確保軟管和線路布置正確，應并遠離排氣部件或移動部件。
在壓縮配件，以及動力轉向泵和齒輪連接，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動的，那么檢查帶的磨損或損壞情況。與類似的車輛相比，聽泵是否有異常的噪音。一個噪雜的泵是存在一個問題的明確指示，不管這問題本身就是是一個錯誤還是像空氣一樣的東西被誘導到系統(tǒng)中而導致的錯誤。被吸進系統(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致泵過早出現(xiàn)故障。
當然，驅動器的整個系統(tǒng)是方向盤。不管是什么樣的設計一定要經(jīng)常檢查轉向連桿，從齒輪直至轉向柱，包括其中任何設計的連接件。大多數(shù)系統(tǒng)裝有一系列的萬向節(jié)，滑軛，擠壓軸或某種類型的中間轉向軸，使齒輪連接成一列。這是要做的最后一件事來防止車子以65英里每小時在高速上行駛時發(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，很少需要進行維修，但這是轉向系統(tǒng)一個至關重要的部分。軸承列本身的自由旋轉應該被檢查以確保在軸承列中沒有松動存在。
電動動力轉向系統(tǒng)中，通常有一個不可分割的列和一個電動助力設計。這些系統(tǒng)通常作為一個組件替換，在這些部件中除了電子部件外，不會有需要維修的部件。雖然有這樣的說法，但他們應該仍然像任何其他的部件一樣被檢查。
服務仍是答案
正如在汽車上的其他任何一個系統(tǒng)，我們知道轉向助力也需要服務。在任何的轉向系統(tǒng)中都有許多維修的堅硬的部分，但隨著良好的日常維護，大多數(shù)組件將持續(xù)很長一段時間。我們的客戶必須在對像動力轉向系統(tǒng)一樣的系統(tǒng)正常的服務受到教育。
樞軸點和管件在定期間隔維修時應進行潤滑或上油。夾點或轉向站應潤滑良好。當然，我們不要忘記，在液壓系統(tǒng)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。即使流體設計在此種環(huán)境中，但粘度和熱破壞還是會發(fā)生。流體可以開始燃燒和分解，作為組成部分在流體行進的系統(tǒng)中降低，然后污染物開始在流體中慢慢變多。
這些液體應可以有像汽車里任何其他的流體那樣的功用么？當然可以。只需要畫上幾分鐘就可以從系統(tǒng)中抽取一個樣品液體，并檢查它的燃燒和污染。如果燃燒物存在，那么這可能是一個很好的時機來沖洗，清潔和重新填充系統(tǒng)。
在市場上有很多不錯的系統(tǒng)來沖洗和清洗動力轉向系統(tǒng)。有些系統(tǒng)將正確連接地汽車動力轉向系統(tǒng)，而還有一些則通過儲液簡單的提取和重新引入液體和清潔劑。
當然也有一些相當不錯的冷卻裝置也是隨著這些系統(tǒng)而來的。隨著高品質的合成動力轉向液，當涉及到極端條件下的流體時，你可以為你的客戶一個更好的選擇。通過這些產(chǎn)品，我們可以提供良好的服務，可以為客戶節(jié)約了大量的資金，讓他們安心。