Lesson 20 The Hydraulic System and Equipment

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1、Lesson20TheHydraulicSystemandEquipment第20课液压系统和液压设备HydraulicSystems液压系统Hydraulicsystemsaremadeupofanoiltank,pumps,controlvalve,hydraulicmotorandpipework.Theoiltankandpumpiscommontoallequipmentactingasacentralpumpingunit.Threedifferentbasiccircuitsareused,employingeitherlowormedium

2、pressureoilsupplies.液压系统由油箱、油泵、控制阀、液压马达和管路构成。油箱和油泵作为中央泵组，为所有设备公用。无论是低压还是中压供油单元中，都采用三种基本的回路。Theopenloopcircuittakesoilfromthetankandpumpsitthroughacontrolvalveintothehydraulicmotor.Theexhaustoilreturnstothetankandinneutraltheoilbypassesthehydraulicmotor.Thelivelinecircuitmaintainsa

3、highpressurefromwhichthecontrolvalvedrawspressurizedoiltothehydraulicmotorasandwhenrequired.Theclosedloopcircuithastheexhaustoilreturnedtothepumpsuction.Thepumpisofthevariabledeliverytype,providingmaximumflexibilityinoilsupplytotheequipment.Lowpressuresystemsusetheopenloopcircuita

4、ndaresimpleindesignaswellasreliable.Theequipmentishoweverlarge,inefficientinoperationandoverheatsafterprolongeduse.Mediumpressuresystemsarefavoredformarineapplicationsusingeithertheopenorclosedcircuit.Smallerinstallationsareoftheopenloopcircuittype.开式回路从油箱吸油，并经过控制阀将油泵送到液压马达。排油回到油箱

5、，在中位时，经过液压马达油液旁通。在需要的情况下，根据液压系统的要求，控制阀将压力油送至液压马达，这部分液压管路一直保持高压。在闭式回路中排油回到泵的吸入口。油泵是变量式油泵，使得向设备的供油有了极大的灵活性。低压系统多采用开式回路，并且设计简单，工作可靠。然而设备体积大，操作效率低，长时间运行会发热。船用装置中，无论是开式回路还是闭式回路，采用中压系统都是最适合的。小型装置采用开式回路。Manyreasonscanbesuggestedfortheuseofhydraulicsystemsinmarineengineering:轮机工程方面采用液压系统的

6、理由：(a)Aconvenientmethodoftransferringpoweroverrelativelylongdistancesfrom,say,acentralpumproomtoremoteoperatingsitesintheship:wherenecessary,completelocalcontrolofoperationscanbeachieved;A.在相当长的距离上，比如说从船上的中央泵到遥控处所，是方便的传动方式，当必要时可以实现完全的机旁控制。(b)Fullyvariablespeedcontrolofbothlinearan

7、drotarymotion,withgood“inching”capabilityandsmoothtakeupofload;Inallcasespoweriscontinuouslytransmittedwhilstspeedchangestakeplace;B.在直线运动和回转运动上可以实现无级变速，具有良好的微速性能和平稳的负载能力，在任何变速情况下都可以连续地传递动力。(c)Highstaticforcesortorquescanbeachievedandmaintainedindefinitely；C.可以实现并长时间保持静态力或者静扭矩(d)C

8、ompletesafetyandreliabilityisassu