WY270液壓挖掘機工作裝置的設計【含4張CAD圖紙+文檔全套】
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外文資料譯文
On the hydraulic system failure analysis One、
hydraulic system failures outlined
1. Fault of
Hydraulic system failure can be broadly classified into three categories:
1． 1abnormal pressure
General pipeline system designed for a lot of pressure on the measuring point, the use of pressure gauges measured reading, compared with the normal analysis to determine the cause abnormal pressure hydraulic components.
1.1 speed abnormal
By adjusting throttle valve, variable speed control valve and pump variables, testing the implementation of the corresponding components of the speed range, and comparative analysis of the design value can be determined.
1． 2 abnormal movements
Each valve switch to observe the implementation of the relevant components of the state action is normal, you can identify abnormal valve, then check action sequence and travel control, to identify the anomaly.
2. Fault of the commonly used detection method
Hydraulic system condition monitoring and fault diagnosis, including oil sample analysis, system components of the state monitoring and control system status monitoring and fault diagnosis and the reasons for failure analysis and positioning.
Oil-like through the observation and measurement of oil and wear powder contained in the shape, size, colour and quantity, etc., may be accurate hydraulic system of wear and corrosion, identifying the hydraulic system failure type, extent and location. Commonly used method of record iron spectrum, spectral analysis, particle counting and simple comparison of judgement, In addition, some of the content of the air and water testing methods. Apparatus available on-line analysis of oil samples, access to oil Pollution of the information.
System components of the state monitoring system components of the vibration and noise analysis of the information system can work status, and diagnosis can be the cause of the malfunction of hydraulic components and parts. Measurement of vibration signals the general acceleration sensor, the hydraulic system of hydraulic pumps and some obvious vibration Shell hydraulic valve, by measuring the shell of vibration signals to determine their work status. Commonly used hydraulic equipment vibration diagnostic methods :
(1)-square-frequency vibration amplitude of the restrictions: the detection of hydraulic components shell vibration signals, calculate the square-frequency amplitude, when the closure provisions of this value is greater than the value when tested components can be judged for the failure狀態(tài).
(2) characteristic frequency of law: the use of hydraulic components measured vibration signal spectrum, with the normal vibration signal spectrum, according to their differences in determining the fault location, type, extent and causes.
(3) a signal frequency domain of technology: the signal frequency and time domain of only the signal from a certain area to analyze, from the vibration signal characteristics. In many occasions, the frequency of the signal characteristics and the time-related. This requires a time-frequency signal analysis, vibration signals from the time a frequency of two angles access to feature information. At present, the use of wavelet (Wavelet) transformation of non-stationary signals in the characteristics of the information collected is unique advantages.
Control system monitoring and fault diagnosis for the electro-hydraulic servo system, in particular mill hydraulic system as the representative of the AGC, the complex structure, set machine, power, in one of the industrial electro-hydraulic servo system. Step response can be law And random signal frequency response method for monitoring and diagnosis. Step response to the law through the system one step lose signal. Detection of its step-response, and under normal conditions the response of comparison. Determine the system running. Random signal frequency response of the control system to add a weak signal of white noise, by measuring the response of control systems, and the normal transmission characteristics, the system determine the operational status and the reasons for the failure and parts . Surcharge due to weak signal, is available online for diagnosis. The easy way to the mechanical systems, electrical systems separately for diagnosis.
2、 the failure of prevention
1. Guarantee the cleanliness of hydraulic oil
The proper use of the calibration and require the use of hydraulic oil and their corresponding substitutes (in detail the Senate "construction machinery oil manual") to prevent the intrusion of hydraulic oil in the dirt and impurities. Because in the hydraulic system, hydraulic oil is not only working media, but also a lubricant, oil cleanliness of the system performance, the reliability of components, safety, efficiency and service life, and so greatly influenced. Hydraulic components with high precision, the oil in the dirt caused by impurities in the deposition, obstruction, abrasion and corrosion, and other more sensitive response. The dirt impurities penetrated the main hydraulic oil, dirty First, the implementation of external components; Second, check the status of oil do not pay attention to the third is without refueling purposes filter filter 120; Fourth, the use of containers and appliances, not Clean; five is serious wear and damage to the seal can not be promptly replaced; six is to check repairs, Rewan pipeline joints and welding repair the scale of impurities do not clean up the net; seven oil storage is improper, and so on. In the use of the repair process of inspection, attention should be paid to solve these problems, to reduce and prevent the occurrence of hydraulic system failure.
2． To prevent hydraulic oil mixed with air in
The hydraulic system of hydraulic oil can not be compressed, but the air compressibility great system even contains a small amount of air, its influence is very great. Oil dissolved in the air, the pressure is low, it will have escaped from the oil bubbles, formed hole; to the high-pressure area, the impact of the pressure, these bubbles soon be crushed, by a sharp compression , The system generated noise. At the same time, by a sudden gas compression, it will emit a lot of heat and thus cause local heating, hydraulic components and hydraulic oil were damaged, job instability, and sometimes lead to shock vibration.
Therefore, the need to prevent air into the hydraulic system. Specifically: First, to avoid pipeline rupture, loose joints, seal damage and the other is refueling, to avoid improper dumping down the third is to insert the oil-pipeline below four hydraulic pump is to avoid blocking the entrance to Lvyou Qi Range Increased resistance can not be dissolved in oil separated from the air.
3． Hydraulic oil temperature to prevent excessive
Oil hydraulic system in the work of the general temperature in 30 ℃ ~ 80 ℃ within relatively good, must pay attention to preventing the use of excessively high oil temperature. If the fuel tank of oil-enough, hydraulic oil cooler heat dissipation bad, the system efficiency is too low, the capacity of small components, high velocity, the choice of the oil viscosity is not correct, they will make the oil temperature increased too fast. High oil viscosity to increase the flow of energy loss, low viscosity will increase in leakage, in use and check to pay attention to these issues, we can prevent excessive oil temperature. In addition to the regular hydraulic oil filter, regular physical performance test, it can guarantee the performance of the hydraulic system, hydraulic components and reducing the wear and corrosion, oil and hydraulic components to extend the service life.
3、 the exclusion of common fault (for example roller)
The roller hydraulic system monitoring, maintenance personnel experienced by the senses of hearing, touch, see, sniff get important information. Bearing hearing to determine the noise, the screams of relief valve and pump cavitation abnormal pulse of the sound; can be found with their hands touching the hydraulic components overheating and excessive vibration; visually observed that the implementation of the operation, the pressure gauge readings, Jitter and hose leak oil, and so on; Faxiu metamorphic hydraulic oil will lead to a variety of failures, should be immediately replaced. Hydraulic system performance to overheating, noise, vibration and other phenomena, in the early stages of operation of machines over time, may show the machines have not been adversely affected, but these abnormal symptoms must not be taken lightly, once found a timely analysis and should be ruled out.
1． Overheated oil temperature
The hydraulic system of hydraulic oil temperature rise should normally not exceed 40 degrees Celsius. In other words, when the roller in the ambient temperature of 40 degrees Celsius in the work, should not be the highest oil temperature over 80 degrees Celsius, the high oil temperature will lead to decreased viscosity hydraulic oil, spare parts and increase the gap with rubber seals damaged, making Serious leakage of the hydraulic system, unable to drive. Produce excessive heat are many reasons for, in addition to design and manufacture of factors, mainly due to adjustment of components, operation and maintenance of the poor. For example, the surge relief valve too high, a large number of invalid transformed into heat energy consumption; roller walking hydraulic-driven high-pressure, flow, the frequent exchange operations to the oil temperature will suddenly increased hydraulic oil tank Radiator or less fouling too much, the impact of the cooling effect of hydraulic oil.
2. Excessive noise
Hydraulic system in the design and manufacturing process, through reasonable matching components and carefully assembled, as much as possible to eliminate noise causes. The hydraulic system when the work is the main reason for the noise generated within the system caused by the gas mixed with the high-frequency vibration. Hydraulic system, the source of gas, oil pump into the First Circuit impeded the cavity, the reasons are generally: Oil Lvyou Qi obstruction or too small, too small diameter of inhalation, inhalation of a pipe elbow , Inhaled too long pipeline, the oil temperature is too low, not oil, Tongqi Kong too small or blockage, inhaled too much damping piping, pumps fill failures, excessive speed hydraulic pump, a hydraulic pump from the surface High and the other is Hunjin hydraulic oil in the air, the reasons for its general are: low liquid fuel tank, fuel tank design unreasonable, in the fuel tank back to the surface on the pipeline, the oil inappropriate, shaft seal Damage, inhalation of joint leakage, a hose pores, bad exhaust system. To find reasons, to take corresponding measures to troubleshooting.
3．Concussion too large
The hydraulic system is often because of excessive vibration is not strong fixed components (including pumps, valves, motors and pipes installed), the installation of pumps and imbalance within the system mixed with the air, will be accompanied by high-frequency vibration noise. Pumps installed by the imbalance is more flexible connectivity to the shaft and the imbalance caused by bad neutral. Exclude excessive vibration of the main measures is to ensure that the correct installation of hydraulic components and firmly to prevent the intake system.
4． Leak too much
The leakage of hydraulic system performance often fell for the work pressure, a serious leak may occur when the implementation of components to reduce velocity or reptiles. A leak of hydraulic system leak in China and the points of leakage rely on the visual found that the leakage would use pressure or flow meter test can be sure. In addition to the leakage of a small number of components because of pipe damage caused or shell, usually because of the sealing problem. Therefore, maintenance staff should understand the various forms of sealing the working principle and use; replacement of seals, they should pay attention to their material properties, such as whether the size models to meet the requirements; stall the installation lap position to help seal a role to play and increased use of Life; installed seal before it is necessary to seriously clean to prevent dirt mixed; installed seals should be careful to prevent scratches, bites and twisting phenomena such as occurred over the use of thread pinched seals, pinched force To properly size and uniformity. The leakage is more complicated, if not the design of components, then the main reason is in line with gap is too large, the oil seal sealed poor performance or injury, and the use of a dilute the hydraulic oil. A leak in the hydraulic system, the general maintenance of all the replacement components or related components, replacement parts of the hydraulic components should be used after the test bed. If this is the summer high temperatures, the use of the more crowded the hydraulic oil can be overcome to some extent, China.
淺談液壓傳動系統(tǒng)故障分析
一、液壓傳動系統(tǒng)故障概述
1.故障劃分
液壓傳動系統(tǒng)故障可大致分為三類：
1.1壓力異常
一般系統(tǒng)管路設計時預留很多壓力測點，使用壓力表測出讀數(shù)，與正常值比較分析即可確定引起壓力異常的液壓元件。
1.2速度異常
逐一調節(jié)節(jié)流閥、調速閥及變量泵變量機構，對應測試執(zhí)行元件的速度范圍值，與設計值比較分析即可確定。
1.3動作異常
切換每個換向閥，觀察相關執(zhí)行元件的動作狀態(tài)是否正常，即可找出異常換向閥，再檢查動作順序和行程控制，找出異常處。
2.故障的常用檢測方法
液壓系統(tǒng)狀態(tài)監(jiān)測與故障診斷包括油樣分析、系統(tǒng)元件的狀態(tài)監(jiān)測、控制系統(tǒng)狀態(tài)監(jiān)測與故障診斷及故障原因分析與定位等。
油樣分析通過觀察和測量油液中所含磨損粉末的形態(tài)、大小、顏色和數(shù)量等，可準確得到液壓系統(tǒng)的磨損和腐蝕情況，確定液壓系統(tǒng)的故障類型、程度和部位。常用的方法有鐵譜記錄診斷法、光譜分析法、顆粒計數(shù)法和簡易對比判斷法等，此外、還有一些對空氣含量和水分的測試方法.可利用儀器在線分析油樣、獲取有關油液污染度的信息。
系統(tǒng)元件的狀態(tài)監(jiān)測利用系統(tǒng)元件的振動和噪聲信息可以分析系統(tǒng)的工作狀態(tài)、并可以診斷液壓元件的故障原因和部位。振動信號的測量一般采用加速度傳感器，對于液壓系統(tǒng)中的液壓泵及某些殼體振動明顯的液壓閥，通過測量分析殼體振動信號可以確定其工作狀態(tài).常用液壓設備振動診斷方法有：
（1）通頻振動均方幅值越限診斷：檢測液壓元件殼體的振動信號，計算其通頻均方幅值，當此值大于規(guī)定閉值時，可判斷被測元件為故障狀態(tài)。
（2）特征頻率診斷法：用測得的液壓元件振動信號頻譜，與正常振動信號頻譜比較，根據(jù)其差異確定故障的部位、類型、程度和原因。
（3）信號時一頻域診斷技術：信號的頻域和時域分析都只是從信號的某一個方面來分析、抽取振動信號特征。而在許多場合，信號頻率分布的特征與信號發(fā)生的時間相關.這就需要采用信號時頻分布分析技術，從振動信號的時間一頻率兩個角度獲取特征信息。目前、利用小波(Wavelet)變換對非平穩(wěn)信號的特征信息抽取具有獨特優(yōu)點。
控制系統(tǒng)狀態(tài)監(jiān)測與故障診斷對于電液伺服系統(tǒng)，特別是以軋機液壓AGC系統(tǒng)為代表的、結構復雜的、集機、電、液于一體的工業(yè)電液伺服系統(tǒng).可采用階躍響應法和隨機信號頻率響應法進行狀態(tài)監(jiān)測與診斷.階躍響應法通過給系統(tǒng)輸人階躍信號。檢測其階躍響應，并與正常狀態(tài)下的響應特性比較。確定系統(tǒng)的運行狀態(tài).隨機信號頻率響應法是在系統(tǒng)控制信號上加入微弱的白噪聲，通過測量控制系統(tǒng)響應特性、并與正常時的傳遞特性比較，確定系統(tǒng)的運行狀態(tài)及故障的原因和部位.因附加信號很弱，可在線進行診斷。該方法易于對機械系統(tǒng)、電氣系統(tǒng)分開進行診斷。
二、故障的預防
1.保證液壓油的清潔度
正確使用標定的和要求使用的液壓油及其相應的替代品(詳參《工程機械油料手冊》)，防止液壓油中侵入污物和雜質。因為在液壓傳動系統(tǒng)中，液壓油既是工作介質，又是潤滑劑，所以油液的清潔度對系統(tǒng)的性能，對元件的可靠性、安全性、效率和使用壽命等影響極大。液壓元件的配合精度極高，對油液中的污物雜質所造成的淤積、阻塞、擦傷和腐蝕等情況反應更為敏感。造成污物雜質侵入液壓油的主要原因，一是執(zhí)行元件外部不清潔；二是檢查油量狀況時不注意；三是加油時未用120目的濾網(wǎng)過濾；四是使用的容器和用具不潔凈；五是磨損嚴重和損壞的密封件不能及時更換；六是檢查修理時，熱彎管路和接頭焊修產(chǎn)生的銹皮雜質清理不凈；七是油液貯存不當?shù)鹊?。在使用檢查修理過程中，應注意解決這些問題，以減少和防止液壓系統(tǒng)故障的發(fā)生。
2.防止液壓油中混入空氣
液壓系統(tǒng)中液壓油是不可壓縮的，但空氣可壓縮性很大即使系統(tǒng)中含有少量空氣，它的影響也是非常大的。溶解在油液中的空氣，在壓力較低時，就會從油中逸出產(chǎn)生氣泡，形成空穴現(xiàn)象；到了高壓區(qū)，在壓力的沖擊下，這些氣泡又很快被擊碎，急劇受到壓縮，使系統(tǒng)產(chǎn)生噪音。同時，氣體突然受到壓縮時，就會放出大量的熱能，因而引起局部受熱，使液壓元件和液壓油受到損壞，工作不穩(wěn)定，有時會引起沖擊性振動。
故必須防止空氣進入液壓系統(tǒng)。具體做法:一是避免油管破裂、接頭松動、密封件損壞；二是加油時，避免不適當?shù)叵蛳聝A倒；三是回油管插入油面以下；四是避免液壓泵入口濾油器阻塞使吸油阻力增大，不能把溶解在油中的空氣分離出來。
3. 防止液壓油溫度過度
液壓系統(tǒng)中的油液的工作溫度一般在30℃~80℃范圍內比較好，在使用時必須注意防止油溫過高。如油箱中的油面不夠，液壓油冷卻器散熱性能不良，系統(tǒng)效率太低，元件容量小，流速過高，選用油液粘度不正確，它們都會使油溫升高過快。粘度高增加油液流動時的能量損耗，粘度低會使泄漏增多，因此在使用中能注意并檢查這些問題，就可以預防油溫過高。此外對液壓油定期過濾，定期進行物理性能檢驗，既能保證液壓系統(tǒng)的工作性能，又能減少液壓元件的磨損和腐蝕，延長油液和液壓元件的使用壽命。
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三、常見故障的排除（以壓路機為例）
對壓路機液壓系統(tǒng)的監(jiān)控，有經(jīng)驗的維修人員可以通過感官的聽、摸、看、嗅得到重要的信息。聽覺能夠判斷軸承的雜音、溢流閥的尖叫聲及油泵氣蝕的不正常脈動聲； 用手觸摸可發(fā)現(xiàn)液壓元件的過熱和過度振動；視覺可觀察到執(zhí)行機構的運行情況、壓力表讀數(shù)、軟管抖動及滲漏油情況等；發(fā)臭變質液壓油會導致多種故障，應立即更換。液壓系統(tǒng)表現(xiàn)出的過熱、噪聲、振動等現(xiàn)象，在機器運行的初期一段時間內，可能對機器尚未表現(xiàn)出不利影響，但這些異常征兆決不可掉以輕心，一旦發(fā)現(xiàn)應及時分析和排除。
1.油溫過熱
液壓系統(tǒng)液壓油的溫升一般應不超過40攝氏度。也就是說，當壓路機在40攝氏度的環(huán)境溫度中工作時，最高油溫不應超過80攝氏度，過高的油溫會導致液壓油粘度下降、零件配合間隙增加及橡膠密封件損壞，使得液壓系統(tǒng)泄漏嚴重，驅動無力。產(chǎn)生過熱的原因是多方面的，除了設計制造方面的因素之外，主要是由于元件調整、操作和保養(yǎng)不善造成的。例如，溢流閥調壓過高，大量的無效能耗轉化成了熱量；壓路機行走液壓驅動的壓力高、流量大，作業(yè)時頻繁換向會使油溫驟然升高；液壓油箱的油量少或散熱器積垢太多，影響了液壓油的散熱效果。
2.噪聲過大
液壓系統(tǒng)在設計和制造過程中，通過合理選配元件和精心裝配，盡可能地消除噪聲根源。液壓系統(tǒng)工作時產(chǎn)生噪聲的主要原因是系統(tǒng)內混有氣體所引起的高頻振動。液壓系統(tǒng)內氣體的來源，一是油泵進油路不暢造成的氣穴，其產(chǎn)生的原因一般有:進油濾油器阻塞或過小、吸入管直徑過小、吸入管路彎頭過多、吸入管路太長、油液溫度過低、油液不適宜、通氣孔過細或堵塞、吸入管路阻尼太大、補油泵故障、液壓泵轉速過高、液壓泵距液面過高；二是液壓油中混進了空氣，其產(chǎn)生的原因一般有:油箱液面太低、油箱設計不合理、油箱中回油管在液面之上、油液不合適、泵軸油封損壞、吸入管接頭漏氣、軟管有氣孔、系統(tǒng)排氣不良。找到原因后，采取相應措施即可排除故障。
3.震蕩過大
液壓系統(tǒng)的過度振動往往是由于元件固定不牢(包括泵、閥、馬達及管道安裝)、油泵安裝不平衡及系統(tǒng)內混有空氣造成的，高頻振動還會伴有響聲。油泵安裝的不平衡多是由柔性聯(lián)接的不平衡及泵軸對中性不好引起的。排除過度振動的措施主要是確保液壓元件安裝正確而牢固，防止系統(tǒng)進氣。
4.泄漏過大
液壓系統(tǒng)的泄漏往往表現(xiàn)為工作壓力下降，泄漏嚴重時可能出現(xiàn)執(zhí)行元件運動速度降低或爬行。液壓系統(tǒng)泄漏有外泄和內泄之分，外泄漏可憑人的視覺發(fā)現(xiàn)，內泄漏則需用儀表測試壓力或流量才能肯定。外泄漏除了少數(shù)會因為元件殼體或管道破損引起之外，一般都是因密封問題產(chǎn)生的。所以維修人員應該了解各種形式密封的工作原理及使用方法；更換密封件時，應注意其材質性能、型號尺寸等是否符合要求；檔圈的安裝位置要有助于密封件發(fā)揮作用和增加使用壽命；安裝密封件之前，要認真清洗干凈，以防污物混入；安裝密封件時應仔細，防止被劃傷、咬傷及翻扭等現(xiàn)象發(fā)生；使用螺紋壓緊的密封件，壓緊力大小要得當并均勻。內泄漏情況比較復雜，如果不計元件的設計因素，那么最主要的原因是配合間隙過大，油封的密封性能差或損傷，以及使用了過稀的液壓油。液壓系統(tǒng)出現(xiàn)內泄漏時，一般的維修方法都是更換元件或有關零件，更換過零件的液壓元件應經(jīng)臺架試驗后方可使用。如果是夏季高溫天氣，使用較稠的液壓油也能在一定程度上克服內泄。
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