液压传动试卷计算题答案

1.Inthehydraulicsystembelow,twocylindersareinseriesandthepressurizedoilissuppliedbythepump.Thesetwohydrauliccylindershavethesamesize,thediameterofthepistonD=90mm,thediameterofthepistonrodd=60mm.TheactingforcesF1=F2=10000N,theflowrateofthepumpQ=25L/min.Neglectingtheleakageandotherpressureloss,pleasecalculatetheoutputpressureofthehydraulicpumpandmovingspeedofthepiston.如图所示，两个液压缸串联，由一台液压泵驱动。已知两液压缸尺寸相同，缸体内径D=90mm，活塞缸直径D=90mm，活塞杆直径d=60mm，负载力,流量泵流量Q=25L/min。若不计容积损失和机械损失，求液压泵的输出压力和活塞运动速度。解：由活塞受力平衡方程得所以液压泵输出压力活塞运动速度2.Inthefollowingvariabledisplacementpump-fixeddisplacementmotorhydraulicsystem,thesettingpressureofthereleilefvalvepYis0.4MPa,themaximumdisplacementofthepumpVpmax=100mL/r,therotatingspeedofthevariabledeliverypumpnpis1000r/min.Thevolumetricefficiencyofvariabledisplacementpumpηpv=0.9,andthemechanicalefficiencyofthepumpηpmare0.85.ThedisplacementofthemotorVM=50mL/r,thevolumetricefficiencyofvariabledisplacementmotorηMV=0.95,andthemechanicalefficiencyofthepumpηMmare0.9.Neglectingtheleakageandotherpressureloss.IftheoutputtorqueofthemotorisTM=40N.m,therotatingspeedofthevariabledeliverymotornMis160r/min,pleasecalculate.ThedisplacementofthepumpVp.TheactualpressureofthethepumpPp;TheinputpowerofthepumpVpi.如图所示变量泵和定量液压马达系统，液压泵输出压力0.4MPa，变量泵最大排量为=100mL/r,转速为=1000r/min，容积效率=0.9，机械效率=0.85。马达的相应参数为=50mL/r,=0.95,=0.9。不计管道损失，试求当马达的输出转矩为=40N.m、转速为=160r/min时，变量泵的排量、工作压力和输入功率。解：变量泵排量 变量泵工作压力等于马达进口压力，即 变量泵输入功率 3.Inthehydraulicsystembelow,theeffectiveareaofnon-rodchamberA1=100cm2，theeffectiveareaoftherodchamberA2=50cm2.TheminimumdifferentialpressureofthespeedregulatingvalveMPa.Whentheactingforceincreasesfrom0to30000N,thepistonalwaysmovestowardrightandthemovingspeedkeepsthesame.Pleasecalculate:(1)TheminimumsettingpressureofthevalvereliefvalvepY(2)WhentheactingforceF=0,theactualpressureofthepumpandthereturnoilpressureofcylinder.图示回路，已知液压缸两腔面积，，调速阀最小压差为，当负载F从0变化到30000N时，活塞向右运动的速度稳定不变。试求：（1）溢流阀最小调整压力；（2）负载F=0时，泵的工作压力及液压缸回油腔压力。解：（1）溢流阀最小调整压力应根据系统最大负载及调速阀正常工作所需的最小压力差来确定。活塞受力平衡方程：所以（2）回油节流路调速工作时，溢流阀处于常开状态，起定压作用，所以，负载F=0时，泵的工作压力仍为溢流阀调定值，即由活塞受力平衡方程知，当时，液压缸回油腔压力达到最大值。4.Inthehydraulicsystembelow,therotatingspeedofthevariabledeliverypumpnpis1200r/min,thedisplacementofthepumpVPvariesfrom0to8cm3/r.Thesettingpressureofthesafetyvalveis4MPa.ThedisplacementofthemotorVMvariesfrom4cm3/rto12cm3/r.Neglectingtheleakageandotherpressureloss.(1)IftherotatingspeedofthevariabledeliverymotornMis200r/min,pleasecalculatethemaximumoutputpowerofthishydraulicsystemT1,andthemaximumoutputpowerofthethissystemP1.(2)IftherotatingspeedofthevariabledeliverymotornMis400r/min,pleasecalculatethemaximumoutputpowerofthishydraulicsystemT2,andthemaximumoutputpowerofthethissystemP2.如图所示的回路中，变量泵的转速=1200r/min，=0~8cm3/r；安全阀调定压力为p=4MPa；变量马达排量=4cm3/r~12cm3/r。试求马达转速=200r/min和400r/min时，该装置输出的最