599 雙鉸接剪叉式液壓升降臺的設計

599 雙鉸接剪叉式液壓升降臺的設計,鉸接,剪叉式,液壓,升降臺,設計 外文資料翻譯1EXTENDING BEARING LIFEAbstract：Nature works hard to destroy bearings, but their chances of survival can be improved by following a few simple guidelines. Extreme neglect in a bearing leads to overheating and possibly seizure or, at worst, an explosion. But even a failed bearing leaves clues as to what went wrong. After a little detective work, action can be taken to avoid a repeat performance.Keywords: bearings failures lifeBearings fail for a number of reasons，but the most common are misapplication，contamination，improper lubricant，shipping or handling damage，and misalignment. The problem is often not difficult to diagnose because a failed bearing usually leaves telltale signs about what went wrong．However，while a postmortem yields good information，it is better to avoid the process altogether by specifying the bearing correctly in The first place．To do this，it is useful to review the manufacturers sizing guidelines and operating characteristics for the selected bearing.Equally critical is a study of requirements for noise, torque, and runout, as well as possible exposure to contaminants, hostile liquids, and temperature extremes. This can provide further clues as to whether a bearing is right for a job.1 Why bearings failAbout 40% of ball bearing failures are caused by contamination from dust, dirt, shavings, and corrosion. Contamination also causes torque and noise problems, and is often the result of improper handling or the application environment．Fortunately, a bearing failure caused by environment or handling contamination is preventable，and a simple visual examination can easily identify the cause．Conducting a postmortem il1ustrates what to look for on a failed or failing bearing．Then，understanding the mechanism behind the failure, such as brinelling or fatigue, helps eliminate the source of the problem.Brinelling is one type of bearing failure easily avoided by proper handing and assembly. It is characterized by indentations in the bearing raceway caused by shock loading－such as when a bearing is dropped-or incorrect assembly. Brinelling usually 外文資料翻譯2occurs when loads exceed the material yield point(350,000 psi in SAE 52100 chrome steel)．It may also be caused by improper assembly, Which places a load across the races．Raceway dents also produce noise，vibration，and increased torque.A similar defect is a pattern of elliptical dents caused by balls vibrating between raceways while the bearing is not turning．This problem is called false brinelling. It occurs on equipment in transit or that vibrates when not in operation. In addition, debris created by false brinelling acts like an abrasive, further contaminating the bearing. Unlike brinelling, false binelling is often indicated by a reddish color from fretting corrosion in the lubricant.False brinelling is prevented by eliminating vibration sources and keeping the bearing well lubricated. Isolation pads on the equipment or a separate foundation may be required to reduce environmental vibration. Also a light preload on the bearing helps keep the balls and raceway in tight contact. Preloading also helps prevent false brinelling during transit.Seizures can be caused by a lack of internal clearance, improper lubrication, or excessive loading. Before seizing, excessive, friction and heat softens the bearing steel. Overheated bearings often change color，usually to blue-black or straw colored．Friction also causes stress in the retainer，which can break and hasten bearing failure．Premature material fatigue is caused by a high load or excessive preload．When these conditions are unavoidable，bearing life should be carefully calculated so that a maintenance scheme can be worked out．Another solution for fighting premature fatigue is changing material．When standard bearing materials，such as 440C or SAE 52100，do not guarantee sufficient life，specialty materials can be recommended. In addition，when the problem is traced back to excessive loading，a higher capacity bearing or different configuration may be used．Creep is less common than premature fatigue．In bearings．it is caused by excessive clearance between bore and shaft that allows the bore to rotate on the shaft．Creep can be expensive because it causes damage to other components in addition to the bearing．0ther more likely creep indicators are scratches，scuff marks，or discoloration to shaft and bore．To prevent creep damage，the bearing housing and shaft fittings should be visually checked．Misalignment is related to creep in that it is mounting related．If races are misaligned or cocked．The balls track in a noncircumferencial path．The problem is incorrect mounting or tolerancing，or insufficient squareness of the bearing mounting 外文資料翻譯3site．Misalignment of more than 1/4·can cause an early failure．Contaminated lubricant is often more difficult to detect than misalignment or creep． Contamination shows as premature wear．Solid contaminants become an abrasive in the lubricant．In addition。insufficient lubrication between ball and retainer wears and weakens the retainer．In this situation，lubrication is critical if the retainer is a fully machined type．Ribbon or crown retainers，in contrast，allow lubricants to more easily reach all surfaces． Rust is a form of moisture contamination and often indicates the wrong material for the application．If the material checks out for the job，the easiest way to prevent rust is to keep bearings in their packaging，until just before installation．2 Avoiding failuresThe best way to handle bearing failures is to avoid them．This can be done in the selection process by recognizing critical performance characteristics．These include noise， starting and running torque，stiffness，nonrepetitive runout，and radial and axial play．In some applications, these items are so critical that specifying an ABEC level alone is not sufficient．Torque requirements are determined by the lubricant，retainer，raceway quality(roundness cross curvature and surface finish)，and whether seals or shields are used． Lubricant viscosity must be selected carefully because inappropriate lubricant，especially in miniature bearings，causes excessive torque．Also，different lubricants have varying noise characteristics that should be matched to the application. For example，greases produce more noise than oil．Nonrepetitive runout(NRR)occurs during rotation as a random eccentricity between the inner and outer races，much like a cam action．NRR can be caused by retainer tolerance or eccentricities of the raceways and balls．Unlike repetitive runout, no compensation can be made for NRR.NRR is reflected in the cost of the bearing．It is common in the industry to provide different bearing types and grades for specific applications．For example，a bearing with an NRR of less than 0.3um is used when minimal runout is needed，such as in disk—drive spindle motors．Similarly ，machine —tool spindles tolerate only minimal deflections to maintain precision cuts．Consequently, bearings are manufactured with low NRR just for machine-tool applications．Contamination is unavoidable in many industrial products，and shields and seals are commonly used to protect bearings from dust and dirt．However，a perfect bearing seal is 外文資料翻譯4not possible because of the movement between inner and outer races．Consequently ，lubrication migration and contamination are always problems．Once a bearing is contaminated, its lubricant deteriorates and operation becomes noisier．If it overheats，the bearing can seize．At the very least，contamination causes wear as it works between balls and the raceway，becoming imbedded in the races and acting as an abrasive between metal surfaces．Fending off dirt with seals and shields illustrates some methods for controlling contamination．Noise is as an indicator of bearing quality．Various noise grades have been developed to classify bearing performance capabilities．Noise analysis is done with an Anderonmeter, which is used for quality control in bearing production and also when failed bearings are returned for analysis. A transducer is attached to the outer ring and the inner race is turned at 1,800rpm on an air spindle. Noise is measured in andirons, which represent ball displacement in μm/rad.With experience, inspectors can identify the smallest flaw from their sound. Dust, for example, makes an irregular crackling. Ball scratches make a consistent popping and are the most difficult to identify. Inner-race damage is normally a constant high-pitched noise, while a damaged outer race makes an intermittent sound as it rotates.Bearing defects are further identified by their frequencies. Generally, defects are separated into low, medium, and high wavelengths. Defects are also referenced to the number of irregularities per revolution.Low-band noise is the effect of long-wavelength irregularities that occur about 1.6 to 10 times per revolution. These are caused by a variety of inconsistencies, such as pockets in the race. Detectable pockets are manufacturing flaws and result when the race is mounted too tightly in multiplejaw chucks.Medium-hand noise is characterized by irregularities that occur 10 to 60 times per revolution. It is caused by vibration in the grinding operation that produces balls and raceways. High-hand irregularities occur at 60 to 300 times per revolution and indicate closely spaced chatter marks or widely spaced, rough irregularities.Classifying bearings by their noise characteristics allows users to specify a noise grade in addition to the ABEC standards used by most manufacturers. ABEC defines physical tolerances such as bore, outer diameter, and runout. As the ABEC class number increase (from 3 to 9), tolerances are tightened. ABEC class, however, does not specify other bearing characteristics such as raceway quality, finish, or noise. Hence, a noise classification helps improve on the industry standard.外文資料翻譯5無錫職業(yè)技術學院畢業(yè)設計說明書I雙鉸接剪叉式液壓升降臺的設計摘要：雙鉸接剪叉式升降臺的設計是在原由的剪叉式升降臺的基礎上，運用現在的靈活性、安全性、經濟性等指標；結構以能夠滿足靈活性要求較高的汽車維修需要為前提,通過不同型號和響應福建達到滿足物流、汽車維修等性能要求。通過對雙鉸接剪叉式升降臺機構位置參數和動力參數的技術，結合具體實例，對機構中良種液壓缸布置方式分析比較，并根據要求對液壓傳動系統個部分進行設計計算最終確定液壓執(zhí)行元件-液壓缸，通過對叉桿的各項受力分析確定臺板與叉桿的載荷要求，最終完成剪叉式液壓升降臺的設計要求。關鍵字：升降臺；剪叉式 ；液壓Double-hinged scissors hydraulic lifting platform design Abstract: Double-hinged scissors lifts in the design of the previously scissors lifts on the basis of the present application flexibility, security, economic and other indicators, structural flexibility to meet higher requirements of vehicle maintenance the need for premise, and the response by different models to meet Fu jian logistics, vehicle maintenance, and other performance requirements. Through the double-hinged scissors lifts Position parameter and the dynamic parameters of technology, combined with specific examples, the agency improved in the hydraulic cylinder layout analysis and comparison, and in accordance with the requirements of part of a hydraulic system design and calculation of final Pressure implementation components - hydraulic cylinder, through analysis of the fork-defined plate and fork-load requirements, the final completion of scissors hydraulic lifts the design requirements.Key Words：C age assembly； Scissors forks are dyadic； Hydraulic pressure無錫職業(yè)技術學院畢業(yè)設計說明書II目 錄第一章 緒 論························································ 11.1 舉升機的發(fā)展簡史·····················································11.2 汽車舉升機的設計特點···············································21.3 汽車舉升機的安全保證措施···········································31.3.1 設計制造方面的安全保證措施······································· 31.3.2 使用維護方面的安全保證措施······································· 4第二章 剪叉式升降臺的應用及其受力分析的討論························· 52.1 剪叉式升降平臺的三種結構形式······································· 52.2 雙鉸接剪叉式升降平臺機構的位置參數計算··························· 62.3 雙鉸接剪叉式升降平臺機構的動力參數計算··························· 82.4 剪叉式升降平臺機構設計時應注意的問題······························92.5 針對性比較小實例：··················································· 92.6 雙鉸接剪叉式升降平臺機構中兩種液壓缸布置方式的分析比較········· 12無錫職業(yè)技術學院畢業(yè)設計說明書III2.6.1 問題的提出：························································· 132.6.2 兩種布置方式的分析和比較：········································· 142.6.3 實例計算···························································· 15第三章液壓傳動系統的設計計算·········································· 203.1 明確設計要求 制定基本方案：········································· 203.2 制定液壓系統的基本方案·············································· 203.2.1 確定液壓執(zhí)行元件的形式···········································203.2.2 確定液壓缸的類型·················································· 223.2.3 確定液壓缸的安裝方式·············································· 223.2.4 缸蓋聯接的類型····················································· 223.2.5 擬訂液壓執(zhí)行元件運動控制回路····································· 223.2.6 液壓源系統·························································· 22無錫職業(yè)技術學院畢業(yè)設計說明書IV3.3 確定液壓系統的主要參數·············································· 233.3.1 載荷的組成與計算：·················································· 233.3.2 初選系統壓力························································ 253.3.3 計算液壓缸的主要結構尺寸·········································· 263.3.4 確定液壓泵的參數··················································· 283.3.5 管道尺寸的確定···················································303.3.6 油箱容量的確定····················································· 313.4 液壓缸主要零件結構、材料及技術要求································ 313.4.1 缸體································································· 313.4.2 活塞································································· 323.4.3 活塞桿······························································ 333.4.4 活塞桿的導向、密封和防無錫職業(yè)技術學院畢業(yè)設計說明書V塵·········································· 333.4.5 液壓缸的排氣裝置··················································· 343.4.6 液壓缸安裝聯接部分的型式及尺寸··································· 353.4.7 繪制液壓系統原理圖················································· 35第四章 臺板與叉桿的設計計算···········································394.1 確定叉桿的結構材料及尺寸···········································394.2 橫軸的選取···························································· 43結 論································································· 44致 謝································································· 45參考文獻································································· 46畢 業(yè) 設 計 任 務 書200 8 年 2 月 19 日畢業(yè)設計題目 雙鉸接剪叉式液壓升降臺的設計指導教師 曾文萱 職稱 講師專業(yè)名稱 機電一體化技術 班級 機電 50532學生姓名 劉 勇 學號 5020053215設計要求1.完成資料翻譯一份（3000 字以上）2.完成畢業(yè)設計調研報告一份；3.完成雙鉸接剪叉式液壓升降臺的設計4.完成系統程序設計；5.完成畢業(yè)設計說明書一份；6.完成相關圖紙。序號 內容 時間安排1 外文資料翻譯2008.2.20 至2008.2.292 搜集相關資料并調研，完成調研報告2008.3.1 至2008.3.53 進行液壓升降臺各結構的設計，并完成相關系統程序的編寫，編寫說明書，繪制相關圖紙。2008.3.6 至 2008.4.84 整理畢業(yè)設計說明書并定稿，準備答辯2008.4.9 至2008.4.10完成畢業(yè)課題的計劃安排5 答辯 2008.4.11答辯提交資料 外文資料翻譯，畢業(yè)設計調研報告， 畢業(yè)設計說明書，相關圖紙。計劃答辯時間 2007.4.12無錫職業(yè)技術學院機電技術學院2008 年 2 月 19 日分類號 密級 無錫職業(yè)技術學院畢業(yè)設計說明書題 目：雙鉸接剪叉式液壓升降臺的設計英文并列題目：Double-hinged scissors hydraulic lifting platform design學 生 姓 名： 劉勇 專 業(yè)： 機電一體化技術 指 導 教 師： 曾文萱 職 稱： 講師 畢業(yè)設計說明書提交日期 2008.4.11 地址：機電學院