梯形螺纹的计算_新闻中心_济宁利兴精密机械制造有限公司_主营直线导轨,大型丝杠,梯形丝杆,花键轴,丝杠副

梯形螺纹的计算

2012-12-04 点击:52

设计的原始数据是；**起重量Q=60KN和**提升高度H=230mm。 <div align="center"> <table border="1" cellspacing="0" cellpadding="0"> <tbody> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 项目 </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 计算及说明 </td> <td width="95" style="border:solid black 1.0pt;"> 结果 </td> </tr> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 1.螺杆的设计与计算 1.1螺杆螺纹类型的选择 1.2选取螺杆的材料 1.3确定螺杆直径 </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 螺纹有矩形、梯形与锯齿形，千斤顶常用的是梯形螺纹。 梯形螺纹牙型为等腰梯形，牙形角α=30º，梯形螺纹的内外螺纹以锥面贴紧不易松动；它的基本牙形按GB/T5796.1—2005的规定。千斤顶的自锁行能要好，所以用单线螺纹。 因此选用的螺杆螺纹是牙形角α=30º的单线梯形螺纹。 螺杆材料常用Q235、Q275、40、45、55等。 在此选用的是Q275 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。   滑动螺旋的耐磨性计算，主要是限制螺纹工作面上的压力p，使其小于材料的许用压力[p]。 对于等腰梯形螺纹，，有<img width="101" height="49" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image004.gif" />，<img width="13" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image006.gif" />一般取1.2~3.5,所以此处<img width="13" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image006.gif" />取1.5 许用压力[p]取为20MPa。 螺杆螺纹中径<img width="187" height="47" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image009.gif" />，根据求得的此螺纹中径，查表GB/T5796.3—2005取： 公称直径<img width="71" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image011.gif" />，螺距<img width="64" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image013.gif" />，螺杆小径<img width="76" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image015.gif" />，螺杆中径<img width="91" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image017.gif" />。 </td> <td width="95" style="border:solid black 1.0pt;"> 牙形角α=30º的单线梯形螺纹 螺杆材料：Q275 <img width="13" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image006.gif" />=1.5 [p]=10MPa 螺杆尺寸： P=7mm <img width="71" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image011.gif" /> <img width="76" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image015.gif" /> <img width="89" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image021.gif" /> </td> </tr> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 项目 </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 计算及说明 </td> <td width="95" style="border:solid black 1.0pt;"> 结果 </td> </tr> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 1.4自锁验算 1.5结构（见图1―2） </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 自锁条件是λ≤φv 式中：λ为螺纹中径处升角；φv为摩擦角（非矩形螺纹应为当量摩擦角φv=tg-1fv，为保证自锁，螺纹中径处升角至少要比摩擦角小1°。即φv－λ≥l° <img width="111" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image023.gif" /> <img width="277" height="45" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image025.gif" /> <img width="272" height="44" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image027.gif" /> 符合自锁条件。 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，dk≥dp十0.5mm。由后面的计算可知手柄的直径<img width="21" height="25" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image029.gif" />=29mm，所以<img width="157" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image031.gif" />。 <img width="264" height="478" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image033.jpg" align="left" />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小。<img width="77" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image035.gif" />。 退刀槽的宽度可取为1.5P=10.5mm。 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)<img width="141" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image037.gif" />，挡圈用紧定螺钉(GB/T68-2000)<img width="57" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image039.gif" />固定在螺杆端部。 </td> <td width="95" style="border:solid black 1.0pt;"> <img width="80" height="17" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image041.gif" /> <img width="61" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image043.gif" /> <img width="64" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image045.gif" /> <img width="73" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image047.gif" /> 符合自锁条件 <img width="80" height="22" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image049.gif" /> <img width="77" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image035.gif" /> 1.5P=10.5mm 挡环 <img width="129" height="20" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image051.gif" />=5mm 紧定螺钉 <img width="57" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image039.gif" /> </td> </tr> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 项目 </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 计算及说明 </td> <td width="95" style="border:solid black 1.0pt;"> 结果 </td> </tr> <tr> <td width="95" valign="top" style="border:solid black 1.0pt;"> 1.6螺杆强度计算 1.7稳定性计算 </td> <td width="529" valign="top" style="border:solid black 1.0pt;"> 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)，其中扭矩<img width="140" height="43" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image054.gif" />，式中<img width="16" height="17" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image056.gif" />为螺纹中径处升角，<img width="20" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image058.gif" />为当量摩擦角。 对受力较大的螺杆应根据第四强度理论交合螺杆强度： <img width="277" height="51" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image060.gif" />或<img width="191" height="51" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image062.gif" /> F（N）螺杆所受的轴向压；A（<img width="35" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image064.gif" />）：螺杆螺纹的危险截面面积； <img width="23" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image066.gif" />（<img width="35" height="21" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image064.gif" />）：螺杆螺纹段的抗扭截面系数；<img width="17" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image069.gif" />（mm）螺杆螺纹小径；T（<img width="55" height="19" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image071.gif" />）；[s](MPa)：螺杆材料的许用应力，由前面可知螺杆的材料是55号钢，查表得其屈服强度<img width="95" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image073.gif" />，所以其许用应力<img width="76" height="43" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image075.gif" />，由于千斤顶的载荷是稳定的，许用应力取**值有<img width="183" height="43" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image077.gif" />。 计算：<img width="368" height="61" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image079.gif" /> 则有：<img width="231" height="51" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image081.gif" /> <img width="64" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image083.gif" />，符合强度计算的条件。 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稳定性，计算时应注意正确确定螺杆长度系数μ。 当螺杆的柔度λs＜40时，可以不必进行稳定性校核。 长度系数<img width="16" height="17" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image085.gif" />=0.6 螺杆危险截面的惯性半径<img width="91" height="41" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image087.gif" /> 螺杆工作长度l=270.5mm 则柔度<img width="145" height="41" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image089.gif" /> </td> <td width="95" style="border:solid black 1.0pt;"> <img width="92" height="23" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image091.gif" /> <img width="64" height="24" src="file://C:/DOCUME~1/lenovo/LOCALS~1/Temp/msohtml1/01/clip_image083.gif" />， 符合强度计 算的条件。 螺杆稳定。 </td> </tr> </tbody> </table> </div>