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The prospects for the development of mechanical and hydraulic
With the continuous development of human society, the land could be open resources depleted, the world is gradually turning to the ocean, open and use of marine resources has played an increasingly important role in the development of countries. Disputes between countries and regions of the resulting friction. Since the beginning of the new century, with the ocean reefs and the scramble for resources intensifies, sea lanes security situation deteriorating situation of the competing interests at sea will be more severe, especially in the United States, Japan, Russia, India and other countries for the growth of the Navy adopted a multi- kinds of measures, warlords contend situation. In the era of full implementation of the open sea background conditions, the the Navy shoulder the sacred mission to safeguard national security, to defend its sovereignty, safeguard national maritime rights and interests.
At the same time due to the growing economic situation of our country and our increasingly powerful military technology, and the outside world has gradually close up. However, China has a relatively wide field of ports, maritime transport is the best way to contact the outside world. Maritime traffic will be used in ships, land contact must use the springboard, so I will be the springboard device design. Springboard as their own ship an important part of the ship close to the shore, can be used as the access bridge support equipment.
?? ?Reality we have seen boarding ladder gives us the feeling is very heavy, inconvenient for cruise ships is feasible, but if for aircraft carriers or warships, it certainly does not meet the requirements (once the pier is not it will cause trouble), it is necessary to develop a lightweight and convenient and safe to be able to adapt to a military boarding ladder system, this is my topic have to do to achieve the requirements.
I designed a springboard device not only designed a number of mechanical transmission, hydraulic transmission still in the original basis. With hydraulic drive of the outstanding advantages: easy to implement frequent starting, commutation and variable speed, and less impact on the ship's power plant; inertia, high precision position control; force and torque of the output can be large, but the line speed and the speed can be very low, very small size and weight; wide speed range. Therefore, the hydraulic drive is now widely used in all types of vessels. The issue is China's first aircraft carrier, the hydraulic design of the boarding ladder. Springboard (boarding ladder) is mainly used for warships to the pier and weight limit supplies through or migrate. The boarding ladder system to the electric can also be manually manually by hand pump, the use of the hand pump is designed to prevent the boarding ladder in case of power failure can not be used.
In recent years, China's national economy maintained a momentum of rapid development, major national infrastructure projects in full swing, the sustainable development of domestic agricultural machinery, construction machinery, aviation, railway, highway, automobile, shipbuilding and other industries, strong demand for production and construction will drive the continued growth of the hydraulic technology.
By the early 2000s, the general trend of development of the machinery manufacturing industry as the "four modernizations":
?? ?(1) Flexibility: the process equipment and process route can be applied to the needs of the production of a variety of products, can be applied to the rapid replacement of the process, replace the product needs;
??? (2) Agile: products to market for the shortest preparation time reduction, machinery factory steering mechanism flexibility;
?? ?(3) Intelligent: an important part of the flexible automation, it is a new development and extension of the flexible automation. Humans not only to get rid of the heavy manual labor, but also from the tedious calculations, analysis of mental liberation, in order to have more energy to engage in high-level creative work. The intellectualized promote flexible production system has better judgment and ability to adapt.
??? ?The early 2000s, the upgrading of products will continue to speed up a wide variety of needs increasing. According to the statistics of the United States, Japan and Europe and other developed countries, from 1975 to 1995, the type of mechanical parts increased by 40% to 50%, from 75% to 85% of the staff do not deal directly with the material, turn to deal with the information. 80% to 88% of the activity does not directly increase the value-added products, product process, organization and management of increasingly complex. Design, process preparation work about ordering more than 60% of the total time for the completion of the user. On the other hand, in the fierce market competition, supply and product quality often plays a more important role than price. Agility is a major issue in front of the machinery manufacturing industry. Technically to achieve the flexibility, to bring about change in the organization of production, these are machinery manufacturing enterprises urgent event;
??? (4) information technology: machinery manufacturing industry will no longer matter and energy by means of the power of information to produce value, but by the help of the power of matter and energy production value. Therefore, the information industry and intelligence industry will become the leading industry of the society. Machinery manufacturing will also be led by the information, and the use of advanced production mode, new mechanical manufacturing of advanced manufacturing systems, advanced manufacturing technology and advanced organizational management way. The beginning of the 21st century, an important feature of the machinery manufacturing industry in its globalization, networking, virtualization, intelligent and green environmental protection coordination manufacturing.
I designed a springboard device not only designed a number of mechanical transmission, hydraulic transmission still in the original basis. With hydraulic drive of the outstanding advantages: easy to implement frequent starting, commutation and variable speed, and less impact on the ship's power plant; inertia, high precision position control; force and torque of the output can be large, but the line speed and the speed can be very low, very small size and weight; wide speed range. Therefore, the hydraulic drive is now widely used in all types of vessels.
?? ?A complete hydraulic system consists of five parts, namely, power components, actuators, control components, auxiliary components (Annex), and hydraulic oil.
Power components
The role of the power element is the prime mover mechanical energy is converted into fluid pressure, means of pumps in the hydraulic system, it provides power to the entire hydraulic system. Hydraulic pump structure generally in the form of gear pumps, vane pumps and piston pumps.
Actuator
Actuators (such as hydraulic cylinders and hydraulic motors) pressure of the liquid can be converted to mechanical energy to drive the load for linear reciprocating or rotary motion.
Control components
The control element (i.e., the various hydraulic valves to control and regulate the pressure of the liquid, flow rate and direction) in the hydraulic system. According to the different control functions, hydraulic valves can be divided into the pressure control valves, flow control valves and directional control valves. Pressure valve (safety valve) is divided into benefits flow control valve, pressure reducing valves, sequence valves, pressure relay; flow control valve includes a throttle valve, regulating valve, flow diversion valve; directional control valve includes a one-way valve, pilot-operated check valve, shuttle valve, valve. Depending on the control mode, the hydraulic valves can be divided into the switch control valve setpoint control valves and proportional control valve.
Auxiliary components
Auxiliary components including fuel tanks, filters, tubing and fittings, seals, quick-change fittings, high pressure ball valve, hose assemblies, pressure joints, pressure gauge, oil level, oil temperature meter.
Hydraulic oil
The hydraulic oil is the energy transfer in the hydraulic system of the working medium, a variety of mineral oil, emulsion, oil hydraulic molding Hop several categories.
??A little mechanical knowledge all know, the energy will be converted to each other, and to use this knowledge to explain the power loss of the hydraulic system on the hydraulic system is best, however, the hydraulic system power on the one hand will cause energy loss, so that the system the overall efficiency is decreased, on the other hand, lose this part of the energy will be transformed into heat, so that the temperature rise of the hydraulic oil, oil deterioration, resulting in hydraulic equipment failure. Therefore, the design of the hydraulic system, meet the requirements, but also give full consideration to reduce the power loss of the system.
?? ??First, from the power source - pump to consider, taking into account the diversification of the actuator working conditions, high flow, low pressure system sometimes needs; sometimes need small flow and high pressure. So I chose to limit pressure variable displacement pump is appropriate, because this type of pump flow varies with changes in system pressure. When the system pressure is reduced, the flow rate is relatively large, can meet rapid stroke of the actuator. Flow when the system pressure increases and decreases accordingly, to meet the working stroke of the actuator. This will not only meet the requirements of the actuator, but also make more reasonable power consumption.
Second, hydraulic oil flowing through the various types of hydraulic valves inevitable existence of pressure loss and flow losses, account for a large proportion of this part of the energy loss in the total energy loss. Therefore, a reasonable selection hydraulic pressure valve to adjust the pressure is also an important aspect to reduce the power loss. Flow valve system flow adjustment range to select and to ensure that the minimum stable flow to meet the requirements, the pressure of the pressure valve in the hydraulic equipment to meet the normal work of the case, try to take a lower pressure.
??? ?If the actuator has a governor's request, then select the speed control loop, it is necessary to meet the requirements of the governor, but also minimize power loss. Common speed control loop: Throttling Speed ??Control Circuit, volume, speed control loop, the volume throttle speed control loop. Throttling Speed ??loop power loss, low-speed stability. Volume speed control loop is neither overflow losses, no throttling losses, high efficiency, low-speed stability. If you want to meet both requirements at the same time, can be used differential pressure variable volume pump and throttle control Circuits, and to the differential pressure across the throttle as small as possible in order to reduce the pressure loss.
?? ??Fourth, a reasonable choice of hydraulic oil. The hydraulic oil flowing in the pipeline, will appear in the stickiness, while excessive stickiness will be generated when a greater internal friction, resulting in fluid heat, while increasing the resistance to fluid flow. When the viscosity is too low, could easily lead to leakage, and will reduce the volumetric efficiency of the system, therefore, generally choose the suitable viscosity and viscosity-temperature characteristics of good oil. Further, when the fluid flow in the pipeline, but also there is frictional pressure loss and the loss of partial pressure of as short as possible, therefore the design of conduit pipe, while reducing elbow.
??? ?Is to avoid the above referred Some work in the hydraulic system power loss, but the factors affecting the power loss of the hydraulic system there are many, so when the particular design of a hydraulic system needs to be consolidated to consider various other requirements.
1) pollution and wear of components
Oil pollutants caused by the wear and tear of the components of various forms of solid particles into motion pair gap, cutting wear or fatigue wear on the surface of the part. High-speed flow of solid particles on the surface of the impact of the components caused by erosive wear. Oil in the water and oil oxidative deterioration of product components have a corrosive effect. In addition, the oil in the air caused by cavitation, resulting in the element surface erosion and destruction.
2) element clogged with clamping failure
??? ?Based on the parameters measured fault diagnosis system is a hydraulic system is working properly, the key depends on two main operating parameters of pressure and flow is in normal working condition, as well as speed and other parameters of the system temperature and actuators is normal or not. The hydraulic system failure phenomenon is a variety of the cause of the malfunction is a combination of factors. The same factors may cause different symptoms, the same fault may correspond to a variety of different reasons. For example: oil pollution may cause failure of the hydraulic system pressure, flow direction, which brought great difficulties to the hydraulic system fault diagnosis.
??? ?Parameter measurement of fault diagnosis thinking is this, any hydraulic system is working properly, the system parameters to work around the design and setting work if these parameters deviate from the predetermined value, the system will malfunction or may occur malfunction. Hydraulic system failure of the essence of the abnormal changes of the system operating parameters. Therefore, when hydraulic system failure occurs, must be a component of the system or some of the elements of the fault loop a certain point or certain points of the parameter has deviated from a predetermined value, and further it can be concluded. This shows that the operating parameters of a point in the hydraulic circuit is not working properly, the system has a malfunction or failure may occur, require maintenance personnel immediately processed. So on the basis of the parameters measured, combined with logical analysis, you can quickly and accurately identify the fault lies. Parameter measurement method can not only diagnose system failures, but also forecast failures that may occur, and this prediction and diagnosis are quantitative, greatly improving the speed and accuracy of diagnosis. This detection for the direct measurement of speed, and error is small, the testing equipment is simple, easy to promote the use of the production site. Suitable for the detection of any hydraulic system. Measurement without stopping, without damaging the hydraulic system, almost any part of the system to detect not only the existing fault diagnosis and online monitoring, forecasting potential failures.
Parameter measurement principle
??? ?Long as required at any point in the the measured hydraulic system circuit operating parameters will be compared with the normal operation of the system can Analyzing system operating parameters is normal, whether the site where the occurrence of a fault and the fault.
?? ??Hydraulic system operating parameters, such as pressure, flow, temperature, and all non-electrical physical quantity, using indirect measuring method with General Instrument, first of all need to take advantage of the physical effects of these non-power is converted into electricity, and then enlarged, conversion and display The converted electrical signal processing, the measured parameter for availability Representative and displayed. Which can determine the hydraulic system is faulty. However, this indirect measurement methods need a variety of sensors, the detection device is more complex, the measurement error is not intuitive, not easy site to promote the use of.
The advantages of hydraulic
Compared with mechanical transmission, electric drive, hydraulic drive has the following advantages:
????1, the various components of the hydraulic transmission, can be easily and flexibly arranged.
????2, light weight, small size, small inertia, fast response.
????3, manipulation easy to control, can achieve a wide range of variable speed .
????4, automatic overload protection.
????5, generally use mineral oil as the working medium, the relative motion of surface lubrication, long service life.
????6, it is easy to achieve linear motion.
????7, it is easy to realize automation of the machine, not only to achieve a higher degree of automatic control process, when the electro-hydraulic joint control, but also can realize the remote control.
機(jī)械與液壓的發(fā)展前景
隨著人類(lèi)社會(huì)的不斷發(fā)展，陸地可開(kāi)放資源日漸枯竭，世界各國(guó)逐漸將目光轉(zhuǎn)向海洋，海洋資源的開(kāi)放及利用對(duì)各國(guó)的發(fā)展起到了越來(lái)越重要的作用。由此引起的國(guó)家及地區(qū)間爭(zhēng)端、摩擦不斷。進(jìn)入新世紀(jì)以來(lái)，隨著海洋島礁及資源爭(zhēng)奪的加劇，海上運(yùn)輸線安全形勢(shì)日趨惡化，海上利益爭(zhēng)奪的形勢(shì)將更加嚴(yán)峻，尤其是美、日、俄、印等國(guó)家，為壯大海軍采取多種措施，已出現(xiàn)群雄爭(zhēng)鋒的局面。在全面實(shí)施海洋開(kāi)放的時(shí)代背景條件下，海軍肩負(fù)著維護(hù)國(guó)家安全，捍衛(wèi)主權(quán)、維護(hù)國(guó)家海洋權(quán)益的神圣使命。
同時(shí)由于我們國(guó)家日益發(fā)展的經(jīng)濟(jì)情況還有我們?nèi)找鎻?qiáng)大的軍事技術(shù)，我們和外界的聯(lián)系也漸漸的緊密起來(lái)了。但是由于我國(guó)有著較為寬廣的港口領(lǐng)域，所以海上交通便是我們和外界取得聯(lián)系的最好方式。但是海上交通就一定會(huì)用到輪船，而與陸地取得聯(lián)系就一定要用到跳板了，所以我便對(duì)這種跳板裝置進(jìn)行了一些設(shè) 計(jì)。跳板作為自行輪船重要的組成部分，可以在輪船靠近岸邊時(shí)，可以作為被保障裝備通行的橋梁。
現(xiàn)實(shí)當(dāng)中我們看到的登船梯給我們的感覺(jué)是很笨重，不方便，如果用于游船是可行的，但是如果用于航母或軍艦的話，那肯定不能符合使用要求了（一旦碼頭情況不允許那就會(huì)帶來(lái)麻煩），所以必須研制出一種既輕巧方便又安全能適應(yīng)軍用的登船梯系統(tǒng)，這就是我的課題所要做達(dá)到的要求。
我所設(shè)計(jì)的跳板裝置不僅設(shè)計(jì)了一些機(jī)械傳動(dòng)，還在原有的基礎(chǔ)上采用了液壓傳動(dòng)。采用液壓傳動(dòng)的突出優(yōu)點(diǎn)是：易于實(shí)現(xiàn)頻繁的起動(dòng)、換向和變速，且對(duì)船舶電站的影響較??；慣性小、位置控制精度較高；輸出的力和轉(zhuǎn)矩可以很大，但線速度和轉(zhuǎn)速可以很低，體積和重量卻很小；調(diào)速范圍廣。因此，液壓傳動(dòng)現(xiàn)已廣泛應(yīng)用在各類(lèi)船舶上。本課題是我國(guó)首艘航母上液壓登船梯的設(shè)計(jì)。跳板（登船梯）主要用于軍艦與碼頭之間人員及限重物資通過(guò)或遷移。本登船梯系統(tǒng)即可電動(dòng)也可手動(dòng)，手動(dòng)是通過(guò)手搖泵來(lái)實(shí)現(xiàn)的，手搖泵的運(yùn)用是為了防止斷電情況下登船梯不能使用而設(shè)計(jì)的。
近年來(lái)，我國(guó)國(guó)民經(jīng)濟(jì)繼續(xù)保持了快速發(fā)展的態(tài)勢(shì)，國(guó)家重大基礎(chǔ)設(shè)施工程已全面鋪開(kāi)，國(guó)內(nèi)農(nóng)用機(jī)械、工程機(jī)械、航空、鐵路、公路、汽車(chē)、造船等行業(yè)持續(xù)發(fā)展，旺盛的生產(chǎn)建設(shè)需求將帶動(dòng)液壓技術(shù)的持續(xù)增長(zhǎng)。
21世紀(jì)初，機(jī)械制造業(yè)總的發(fā)展趨勢(shì)為“四化”：
（1）柔性化：使工藝裝備與工藝路線能適用于生產(chǎn)各種產(chǎn)品的需要，能適用于迅速更換工藝、更換產(chǎn)品的需要；
（2）敏捷化：使產(chǎn)品推向市場(chǎng)準(zhǔn)備時(shí)間縮為最短，使機(jī)械制造廠機(jī)制能靈活轉(zhuǎn)向；
（3）智能化：柔性自動(dòng)化的重要組成部分，它是柔性自動(dòng)化的新發(fā)展和延伸。人類(lèi)不僅要擺脫繁重的體力勞動(dòng)，而且還要從繁瑣的計(jì)算、分析等腦力勞動(dòng)中解放出來(lái)，以便有更多的精力從事高層次的創(chuàng)造性勞動(dòng)。智能化促進(jìn)柔性化，它使生產(chǎn)系統(tǒng)具有更完善的判斷與適應(yīng)能力。
21世紀(jì)初，產(chǎn)品的更新?lián)Q代將不斷加快，各種各樣的需要不斷增加。據(jù)美國(guó)、日本和歐洲等發(fā)達(dá)國(guó)家的統(tǒng)計(jì)，1975～1995年機(jī)械零件的種類(lèi)增加了40％～50％，而75％～85％的工作人員不直接與材料打交道，轉(zhuǎn)與信息打交道。80％～88％的活動(dòng)不直接增加產(chǎn)品附加值，產(chǎn)品工藝過(guò)程、組織管理日益復(fù)雜化。設(shè)計(jì)、工藝準(zhǔn)備等項(xiàng)工作約占為完成用戶訂貨總時(shí)間的60%以上。另一方面，在激烈的市場(chǎng)競(jìng)爭(zhēng)中，供貨期與產(chǎn)品質(zhì)量往往起著比價(jià)格更為重要的作用。敏捷化已是在機(jī)械制造業(yè)面前的重大課題。在技術(shù)上要實(shí)現(xiàn)柔性化，在生產(chǎn)組織上要實(shí)現(xiàn)變革，這些都是機(jī)械制造企業(yè)刻不容緩的大事；
（4）信息化：機(jī)械制造業(yè)將不再是由物質(zhì)和能量借助于信息的力量生產(chǎn)出價(jià)值，而是由借助于物質(zhì)和能量的力量生產(chǎn)出價(jià)值。因此，信息產(chǎn)業(yè)和智力產(chǎn)業(yè)將成為社會(huì)的主導(dǎo)產(chǎn)業(yè)。機(jī)械制造也將是由信息主導(dǎo)的，并采用先進(jìn)生產(chǎn)模式、先進(jìn)制造系統(tǒng)、先進(jìn)制造技術(shù)和先進(jìn)組織管理方式的全新的機(jī)械制造業(yè)。21世紀(jì)初，機(jī)械制造業(yè)的重要特征表現(xiàn)在它的全球化、網(wǎng)絡(luò)化、虛擬化、智能化以及環(huán)保協(xié)調(diào)的綠色制造等。
我所設(shè)計(jì)的跳板裝置不僅設(shè)計(jì)了一些機(jī)械傳動(dòng)，還在原有的基礎(chǔ)上采用了液壓傳動(dòng)。采用液壓傳動(dòng)的突出優(yōu)點(diǎn)是：易于實(shí)現(xiàn)頻繁的起動(dòng)、換向和變速，且對(duì)船舶電站的影響較??；慣性小、位置控制精度較高；輸出的力和轉(zhuǎn)矩可以很大，但線速度和轉(zhuǎn)速可以很低，體積和重量卻很?。徽{(diào)速范圍廣。因此，液壓傳動(dòng)現(xiàn)已廣泛應(yīng)用在各類(lèi)船舶上。
一個(gè)完整的液壓系統(tǒng)由五個(gè)部分組成，即動(dòng)力元件、執(zhí)行元件、控制元件、輔助元件（附件）和液壓油。
動(dòng)力元件
動(dòng)力元件的作用是將原動(dòng)機(jī)的機(jī)械能轉(zhuǎn)換成液體的壓力能，指液壓系統(tǒng)中的油泵，它向整個(gè)液壓系統(tǒng)提供動(dòng)力。液壓泵的結(jié)構(gòu)形式一般有齒輪泵、葉片泵和柱塞泵。
執(zhí)行元件
執(zhí)行元件(如液壓缸和液壓馬達(dá))的作用是將液體的壓力能轉(zhuǎn)換為機(jī)械能，驅(qū)動(dòng)負(fù)載作直線往復(fù)運(yùn)動(dòng)或回轉(zhuǎn)運(yùn)動(dòng)。
控制元件
控制元件(即各種液壓閥)在液壓系統(tǒng)中控制和調(diào)節(jié)液體的壓力、流量和方向。根據(jù)控制功能的不同，液壓閥可分為壓力控制閥、流量控制閥和方向控制閥。壓力控制閥又分為益流閥(安全閥)、減壓閥、順序閥、壓力繼電器等；流量控制閥包括節(jié)流閥、調(diào)整閥、分流集流閥等；方向控制閥包括單向閥、液控單向閥、梭閥、換向閥等。根據(jù)控制方式不同，液壓閥可分為開(kāi)關(guān)式控制閥、定值控制閥和比例控制閥。
輔助元件
輔助元件包括油箱、濾油器、油管及管接頭、密封圈、快換接頭、高壓球閥、膠管總成、測(cè)壓接頭、壓力表、油位油溫計(jì)等。
液壓油
液壓油是液壓系統(tǒng)中傳遞能量的工作介質(zhì)，有各種礦物油、乳化液和合成型液壓油等幾大類(lèi)。
有一點(diǎn)機(jī)械常識(shí)的人都知道，能量會(huì)互相轉(zhuǎn)換的，而把這個(gè)知識(shí)運(yùn)用到液壓系統(tǒng)上解釋液壓系統(tǒng)的功率損失是最好不過(guò)了，液壓系統(tǒng)功率一方面會(huì)造成能量上的損失，使系統(tǒng)的總效率下降，另一方面，損失掉的這一部分能量將會(huì)轉(zhuǎn)變成熱能，使液壓油的溫度升高，油液變質(zhì)， 導(dǎo)致液壓設(shè)備出現(xiàn)故障。因此，設(shè)計(jì)液壓系統(tǒng)時(shí)，在滿足使用要求的前提下，還應(yīng)充分考慮降低系統(tǒng)的功率損失。
第一，從動(dòng)力源——泵的方面來(lái)考慮，考慮到執(zhí)行器工作狀況的多樣化，有時(shí)系統(tǒng)需要大流量，低壓力；有時(shí)又需要小流量，高壓力。所以選擇限壓式變量泵為宜，因?yàn)檫@種類(lèi)型 的泵的流量隨系統(tǒng)壓力的變化而變化。當(dāng)系統(tǒng)壓力降低時(shí)，流量比較大，能滿足執(zhí)行器的快速行程。當(dāng)系統(tǒng)壓力提高時(shí)流量又相應(yīng)減小，能滿足執(zhí)行器的工作行程。這樣既能滿足 執(zhí)行器的工作要求，又能使功率的消耗比較合理。
第二，液壓油流經(jīng)各類(lèi)液壓閥時(shí)不可避免的存在著壓力損失和流量損失，這一部分的能量損失在全部能量損失中占有較大的比重。因此，合理選擇液壓器，調(diào)整壓力閥的壓力也是 降低功率損失的一個(gè)重要方面。流量閥按系統(tǒng)中流量調(diào)節(jié)范圍選取并保證其最小穩(wěn)定流量能滿足使用要求，壓力閥的壓力在滿足液壓設(shè)備正常工作的情況下，盡量取較低的壓力。
第三，如果執(zhí)行器具有調(diào)速的要求，那么在選擇調(diào)速回路時(shí)，既要滿足調(diào)速的要求，又要盡量減少功率損失。常見(jiàn)的調(diào)速回路主要有：節(jié)流調(diào)速回路，容積調(diào)速回路，容積節(jié)流調(diào) 速回路。其中節(jié)流調(diào)速回路的功率損失大，低速穩(wěn)定性好。而容積調(diào)速回路既無(wú)溢流損失，也無(wú)節(jié)流損失，效率高，但低速穩(wěn)定性差。如果要同時(shí)滿足兩方面的要求，可采用差壓 式變量泵和節(jié)流閥組成的容積節(jié)流調(diào)速回路，并使節(jié)流閥兩端的壓力差盡量小，以減小壓力損失。
第四，合理選擇液壓油。液壓油在管路中流動(dòng)時(shí)，將呈現(xiàn)出黏性，而黏性過(guò)高時(shí)，將產(chǎn)生較大的內(nèi)摩擦力，造成油液發(fā)熱，同時(shí)增加油液流動(dòng)時(shí)的阻力。當(dāng)黏性過(guò)低時(shí)，易造成泄 漏，將降低系統(tǒng)容積效率，因此，一般選擇黏度適宜且黏溫特性比較好的油液。另外，當(dāng)油液