液壓傳動試卷計算題答案

1.Inthehydraulicsystembelow,twocylindersareinseriesandthepressurizedoilissuppliedbythepump.Thesetwohydrauliccylindershavethesamesize,thediameterofthepistonD=90mm,thediameterofthepistonrodd=60mm.TheactingforcesF1=F2=10000N,theflowrateofthepumpQ=25L/min.Neglectingtheleakageandotherpressureloss,pleasecalculatetheoutputpressureofthehydraulicpumpandmovingspeedofthepiston.如圖所示，兩個液壓缸串聯(lián)，由一臺液壓泵驅(qū)動。已知兩液壓缸尺寸相同，缸體內(nèi)徑D=90mm，活塞缸直徑D=90mm，活塞桿直徑d=60mm，負載力,流量泵流量Q=25L/min。若不計容積損失和機械損失，求液壓泵的輸出壓力和活塞運動速度。解：由活塞受力平衡方程得所以液壓泵輸出壓力活塞運動速度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.如圖所示變量泵和定量液壓馬達系統(tǒng)，液壓泵輸出壓力0.4MPa，變量泵最大排量為=100mL/r,轉(zhuǎn)速為=1000r/min，容積效率=0.9，機械效率=0.85。馬達的相應(yīng)參數(shù)為=50mL/r,=0.95,=0.9。不計管道損失，試求當(dāng)馬達的輸出轉(zhuǎn)矩為=40N.m、轉(zhuǎn)速為=160r/min時，變量泵的排量、工作壓力和輸入功率。解：變量泵排量 變量泵工作壓力等于馬達進口壓力，即 變量泵輸入功率 3.Inthehydraulicsystembelow,theeffectiveareaofnon-rodchamberA1=100cm2，theeffectiveareaoftherodchamberA2=50cm2.TheminimumdifferentialpressureofthespeedregulatingvalveMPa.Whentheactingforceincreasesfrom0to30000N,thepistonalwaysmovestowardrightandthemovingspeedkeepsthesame.Pleasecalculate:(1)TheminimumsettingpressureofthevalvereliefvalvepY(2)WhentheactingforceF=0,theactualpressureofthepumpandthereturnoilpressureofcylinder.圖示回路，已知液壓缸兩腔面積，，調(diào)速閥最小壓差為，當(dāng)負載F從0變化到30000N時，活塞向右運動的速度穩(wěn)定不變。試求：（1）溢流閥最小調(diào)整壓力；（2）負載F=0時，泵的工作壓力及液壓缸回油腔壓力。解：（1）溢流閥最小調(diào)整壓力應(yīng)根據(jù)系統(tǒng)最大負載及調(diào)速閥正常工作所需的最小壓力差來確定。活塞受力平衡方程：所以（2）回油節(jié)流路調(diào)速工作時，溢流閥處于常開狀態(tài)，起定壓作用，所以，負載F=0時，泵的工作壓力仍為溢流閥調(diào)定值，即由活塞受力平衡方程知，當(dāng)時，液壓缸回油腔壓力達到最大值。4.Inthehydraulicsystembelow,therotatingspeedofthevariabledeliverypumpnpis1200r/min,thedisplacementofthepumpVPvariesfrom0to8cm3/r.Thesettingpressureofthesafetyvalveis4MPa.ThedisplacementofthemotorVMvariesfrom4cm3/rto12cm3/r.Neglectingtheleakageandotherpressureloss.(1)IftherotatingspeedofthevariabledeliverymotornMis200r/min,pleasecalculatethemaximumoutputpowerofthishydraulicsystemT1,andthemaximumoutputpowerofthethissystemP1.(2)IftherotatingspeedofthevariabledeliverymotornMis400r/min,pleasecalculatethemaximumoutputpowerofthishydraulicsystemT2,andthemaximumoutputpowerofthethissystemP2.如圖所示的回路中，變量泵的轉(zhuǎn)速=1200r/min，=0~8cm3/r；安全閥調(diào)定壓力為p=4MPa；變量馬達排量=4cm3/r~12cm3/r。試求馬達轉(zhuǎn)速=200r/min和400r/min時，該裝置輸出的最