螺旋千斤顶说明书

1、螺旋千斤顶设计计算说明书院 系 工 程 技 术 学 院 专业年级 机械设计制造及其自动化2009级2班设 计 者 王 刚 指导教师 杨 玲 成 绩 2011 年 11 月 28 日螺旋千斤顶设计任务书学生姓名王刚专业年级机械设计制造及其自动化2009级设计题目： 设计螺旋千斤顶设计条件：1、最大起重量F = 65 kN；2、最大升距H =240 mm。设计工作量：1、 绘制出总装配图一张，标注有关尺寸，填写标题栏及零件明细表；2、 编写设计计算说明书一份。指导教师签名： 20 年 月 日目录1螺杆的设计与计算·······&

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4、#183;······31.1螺杆螺纹类型选择·········································&

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6、#183;········31.2选取螺杆材料·······································

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8、83;···················31.3确定螺杆直径·····························

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10、;······························31.4自锁验算··················

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28、3;···········································62.2确定螺母高度H¢及螺纹工作圈数u··

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30、83;·················62.2.1求螺母高度H¢·····························

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32、83;················72.2.2螺纹工作圈数u·······························&#

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34、183;···········72.2.3螺母实际高度H¢···································&

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36、#183;······72.3校核螺纹牙强度·········································&#

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42、183;················································84手柄设计与计

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45、;··················94.1手柄材料······························

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60、83;··13螺旋千斤顶设计计算及说明结果1螺杆的设计与计算1.1螺杆螺纹类型的选择螺纹有矩形、梯形与锯齿形，常用的是梯形螺纹。梯形螺纹牙型为等腰梯形，牙形角=30º，梯形螺纹的内外螺纹以锥面贴紧不易松动。故选梯形螺纹，它的基本牙形按GB/T5796.12005的规定。1.2选取螺杆材料螺杆材料常用Q235、Q275、40、45、55等。1.3确定螺杆直径按耐磨性条件确定螺杆中径d2。求出d2后，按标准选取相应公称直径d、螺距t及其它尺寸。有d2根据国家规定=1.23.5，取=1.2（梯形螺纹）；h=0.5t；查教材表5-12，p取20Mpa。故，d2 = 0.8

61、=41.5mm查机械设计课程设计手册，d取48mm，t=8mm，d1=39mm，d2=44mm1.4自锁验算自锁条件是yrv，式中：y为螺纹中径处升角；rv为当量摩擦角（当量摩擦角rv=arctanmv，但为保证自锁，螺纹中径处升角至少要比当量摩擦角小1°。查教材表5-12，f取0.09y =arctan(t /p d2)=arctan 8/(3.14) =2.88°rv=arctan（f/cos）=arctan 0.09/cos(30°/2)=5.35°则y=2.88°<rv-1°= 4.35°满足自锁条件1.5结构

62、如下图（1-2）:螺杆上端用于支承托杯10并在其中插装手柄7，因此需要加大直径。手柄孔径dk的大小根据手柄直径dp决定，dkdp十0.5mm。为了便于切制螺纹，螺纹上端应设有退刀槽。退刀槽的直径d4应比螺杆小径d1约小0.20.5mm。退刀槽的宽度可取为1.5t。为了便于螺杆旋入螺母，螺杆下端应有倒角或制成稍小于d1的圆柱体。为了防止工作时螺杆从螺母中脱出，在螺杆下端必须安置钢制挡圈(GB/T891-1986)，挡圈用紧定螺钉(GB/T68-2000)固定在螺杆端部。其中：1.5t=12mm d4=38.5mm D13=(1.71.9)d=87mm(1.41.6)d=72mm0.25d=0.2

63、5×48mm=12mmd+(610)=48+8=56mm1.6螺杆强度计算对受力较大的螺杆应根据第四强度理论校核螺杆的强度。强度计算方法参阅教材公式(5-47)，sca=s其中扭矩=65×103×tan(2.88°+5.35°) ×44/2N·mm =206830 N·mm查机械设计课程设计手册，对40钢，=335MPa由表5-13，s=83.75MPad1=39mm，故，sca=62.50MPas=83.75MPa满足强度条件1.7稳定性计算细长的螺杆工作时受到较大的轴向压力可能失稳，为此应按稳定性条件验算螺杆的

64、稳定性。Fcr / F³ 2.5 4螺杆的临界载荷Fcr与柔度s有关，s=ml/i，m为螺杆的长度系数，与螺杆的端部结构有关，l为举起重物后托杯底面到螺母中部的高度，可近似取lH+5t+(1.41.6)d，i为螺杆危险截面的惯性半径，若危险截面面积A=pd12/4，则(I为螺杆危险截面的轴惯性矩)当螺杆的柔度s40时，可以不必进行稳定性校核。计算时应注意正确确定。1.7.1计算柔度（1）计算螺杆危险截面的轴惯性矩I和iI=113560 mm4=9.75mm（2）求起重物后托杯底面到螺母中部的高度llH+5t+(1.41.6)d =240+5×8+1.5×48=35

65、2mm(3)计算柔度查教材表5-14，取2(一端固定，一端自由)查教材公式5-51，E=2.06×105MPas=ml/i=72.2>40，所以需要进行稳定性校核。1.7.2计算稳定性（1）计算临界载荷FcrFcr=465850N(2) 稳定性计算=7.1³ 3.5 5满足稳定性条件。2螺母设计与计算2.1选取螺母材料螺母材料一般可选用青铜，对于尺寸较大的螺母可采用钢或铸铁制造，其内孔浇注青铜或巴氏合金。2.2确定螺母高度H¢及螺纹工作圈数u螺母高度H¢=d2，螺纹工作圈数，考虑退刀槽的影响，实际螺纹圈数u¢ = u+1.5(u¢

66、;应圆整)。考虑到螺纹圈数u越多，载荷分布越不均，故u不宜大于10，否则应改选螺母材料或加大d。螺母高度由下式计算：H¢= u¢t。2.2.1初求螺母高度H¢H¢ =d2=1.2×44=52.8mm2.2.2螺纹工作圈数u=6.6<10，符合要求u¢ = u+1.5 =6.6+1.5=8.1u¢应圆整, u¢取82.2.3螺母实际高度H¢H¢= u¢t=8×8=64mm2.3校核螺纹牙强度一般螺母的材料强度低于螺杆，故只校核螺母螺纹牙的强度。螺母的其它尺寸见图13。必要时还应对螺母外径D3进行强度验算。查教材公式5-48,5-49，螺纹牙的剪切强度和弯曲强度条件分别为：；式中：b为螺纹牙根部的厚度，对于梯形螺纹，b=0.65t;为弯曲力臂，=（D-D2）/2;查机械设计课程设计手册表3-8，D=d+