设计液压专用钻床的液压系统
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湖南农业大学工学院 课程设计说明书
课程名称: 液压与气压传动 题目名称: 设计液压专用钻床的液压系统
班 级:20 级 专业 班 姓 名: 学 号: 指导教师:
评定成绩: 教师评语: 2011-4-30 目录 一、设计要求及设计参数 ·············································································· 3 1、设计要求 ····················································································· 3 2、设计参数 ······················································································· 3 二、负载与运动分析 ···················································································· 3 1、负载分析 ······················································································· 3 A)夹紧缸 ······················································································· 3 B)工作台液压缸 ·············································································· 4 2、运动分析 ······················································································· 4 3、负载图F-t和速度图v-t图的绘制 ························································ 5 三、确定液压系统主要参数 ··········································································· 5 1、液压缸的选定 ················································································· 5 A)夹紧缸 ······················································································· 5 B)工作台液压缸 ·············································································· 5 2、活塞杆稳定性校核 ··········································································· 7 3、液压缸各运动阶段的压力,流量和功率 ··············································· 7 A)夹紧缸 ···················································································· 7 B)工作台液压缸 ··········································································· 8 4、液压缸的工况图 ·············································································· 9 四、拟定液压系统原理图 ·············································································· 10 五、液压元件的选择 ···················································································· 11 1、确定液压泵的规格和电动机的功率 ······················································ 11 2、选择阀类元件及辅助元件 ·································································· 11 六、液压系统发热与升温的验算 ····································································· 12 一、设计要求及设计参数 1.设计要求 设计一台用成型铣刀在加工件上加工出成型面的液压专用铣床,工作循环:手工上料——自动夹紧——工作台快进——铣削进给——工作台快退——夹具松开——手工卸料。 2.设计参数 设计参数如下: 工作台液压缸负载力(KN):FL=9.8KN
工作台液压缸移动件重力(KN):G=2.5 KN 工作台快进、快退速度(m/min):V1=V3=5.5m/min 工作台工进速度(mm/min):V2 =48mm/min 工作台液压缸快进行程(mm):L1 =280mm 工作台液压缸工进行程(mm):L2 =80mm 工作台启动时间(S):t=0.5 s 夹紧液压缸负载力(KN):FC=4.8KN 夹紧液压缸负移动件重力(N):GC=60N 夹紧液压缸行程(mm):LC=10mm 夹紧液压缸运动时间(S):tC=1s 导轨面静摩擦系数:μC=0.2 导轨面动摩擦系数:μd=0.1
FL Fc G Gc V1 V2 L1 L2 Lc tc 9.8 4.8 2.5 60 5.5 48 280 80 10 1
二、负载与运动分析 1、负载分析 A)夹紧缸
工作负载:NGFFdCCl48061.0604800 由于夹紧缸的工作对于系统的整体操作的影响不是很高,所以在系统的设计计算中把夹紧缸的工作过程简化为全程的匀速直线运动,所以不考虑夹紧缸的惯性负载等一些其他的因素。 B)工作台液压缸 1、工作负载 工作负载极为切削阻力FL=9.8KN。 2、摩擦负载 摩擦负载即为导轨的摩擦阻力: (1)静摩擦阻力
NGFcfs50025002.0 (2)动摩擦阻力 NGFdfd25025001.0
3、惯性负载 NDvgGtvgGFti77.465.060/5.58.92500)0(1 4、运动时间 快进 svLt0545.360/105.52803111
工进 svLt667.10660/4580222 快退 svLLt927.360/105.58028033213 假设液压缸的机械效率9.0cm,得出液压缸在各工作阶段的负载和推力,如表1所示。 表1 液压缸各阶段的负载和推力 工况 负载组成 液压缸负载F/N 液压缸推力NFFcm0
启动 fsFF 500 555.56
加速 ifdFFF 296.77 329.74 快进 fdFF 250 277.8 工进 LfdFFF 10050 11166.67 反向启动 fsFF 500 555.56 加速 ifdFFF 296.77 329.74 快退 fdFF 250 277.8
2、运动分析 手工上料—按按钮加紧缸自动加紧—按按钮工作台快进—工作台切削进给—工作台快退—按按钮松开夹具—卸料 3、负载图F-t和速度图v-t图的绘制 三、确定液压系统主要参数 1、液压缸的选定 A)夹紧缸 根据负载选择液压缸的执行压力p=1MPa。
2361081.41014806mpFA mmAD3.781081.4443
根据GB\T2348-1993规定,D取80mm。根据稳定性校核LC/d<10时,液压缸能满足稳定性条件,LC=10mm,,这里取d=40mm。 液压缸的有效作用面积:
有杆腔:2322'11077.34/)(mdDA
无杆腔:232'21003.54/mDA
此时实际工作压力为:MPaMPaAFp1955.0'2,所以选取工作压力1MPa满足要求。 B)工作台液压缸 所设计的动力滑台在工进时负载最大,参考表2和表3,初选液压缸的工作压力p1=2.5MPa.
表2 按负载选择工作压力 负载/KN <5 5~10 10~20 20~30 30~50 >50 工作压力/MPa <0.8~1 1.5~2 2.5~3 3~4 4~5 5
表3各种机械常用的系统工作压力
机械类型 机床 农业机械 小型工程机械 建筑机械 液压凿岩机 液压机 大中型挖掘机 重型机械 起重运输机械
磨床 组合机床 龙门刨床 拉床
工作压力/MPa 0.8~2 3~5 2~8 8~10 10~18 20~32 鉴于动力滑台快进和快退速度相等,这里的液压缸可选用单活塞杆式差动液压缸(A1=2A2),快进时液压缸差动连接。工进时为防止车铣时负载突然消失发生前冲现象,
液压缸的回油腔应有背压,参考表4选定背压为MPap8.02,而液压缸快退时背压取0.5Mpa 由式02211FApAp得
23621011032.510)28.02(67.111662mppFA 则活塞直径 mmmAD3.821023.81415926.31032.544231