1、螺旋千斤頂設(shè)計計算說明書院 系 工程技術(shù)學院 專業(yè)年級 2006級機制班 設(shè) 計 者 XXXXX 指導教師 XXXXX 成 績 2009年4月 1日1 / 23螺旋千斤頂設(shè)計任務書學生姓名XXX專業(yè)年級2006級機械設(shè)計制造及其自動化設(shè)計題目： 設(shè)計螺旋千斤頂設(shè)計條件：1、最大起重量F = 65 kN；2、最大升距H =240 mm。設(shè)計工作量：繪制出總裝配圖一張，標注有關(guān)尺寸，填寫標題欄及零件明細表；編寫設(shè)計計算說明書一份。指導教師簽名： 2009年3月15日目錄1 螺桿的設(shè)計與計算·········&

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29、83;72.2 確定螺母高度H¢及螺紋工作圈數(shù)u·············································&

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44、3;·93 托杯的設(shè)計與計算···············································

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65、83;····················14千斤頂設(shè)計計算和說明 計 算 及 說 明結(jié) 果1螺桿的設(shè)計與計算1.1螺桿螺紋類型的選擇螺紋有矩形、梯形與鋸齒形，常用的是梯形螺紋。梯形螺紋牙型為等腰梯形，牙形角=30º，梯形螺紋的內(nèi)外螺紋以錐面貼緊不易松動。故選梯形螺紋，它的基本牙形按GB/T5796.12005的規(guī)定。1.2選取螺桿材料螺桿材料常用Q235、Q275、40、45、55

66、等。此題選45鋼。1.3確定螺桿直徑按耐磨性條件確定螺桿中徑d2。求出d2后，按標準選取相應公稱直徑d、螺距p及其它尺寸。 d2根據(jù)國家規(guī)定=1.22.5，取=1.4（梯形螺紋）；h=0.5p；查教材表6.5，p取23Mpa故，d2 = = m查機械設(shè)計手冊，d取40mm，則p=7mm， d1=d-8=32mmd4=d1-(0.20.5)=32-0.5=31.5mmd2=d-3.5=36.5mm1.4自鎖驗算選梯形螺紋選45鋼d=40mmp=7mmd1=32mmd4=31.5mmd2=36.5mm自鎖條件是yrv，式中：y為螺紋中徑處升角；rv為當量摩擦角（當量摩擦角rv=arctanmv，為

67、保證自鎖，螺紋中徑處升角至少要比當量摩擦角小1°。查教材表6.7，mv取0.09y =arctan(n p / p d2)=arctan（17/3.1436.5）rv=arctan0.09故，y=3.5°<rv-1°1.5結(jié)構(gòu) 如下圖:螺桿上端用于支承托杯10并在其中插裝手柄7，y=5.14°rv=3.5°因此需要加大直徑。手柄孔徑dk的大小根據(jù)手柄直徑dp決定，dkdp十0.5mm。為了便于切制螺紋，螺紋上端應設(shè)有退刀槽。退刀槽的直徑d4應比螺桿小徑d1約小0.20.5mm。退刀槽的寬度可取為1.5t。為了便于螺桿旋入螺母，螺桿下端應有

68、倒角或制成稍小于d1的圓柱體。為了防止工作時螺桿從螺母中脫出，在螺桿下端必須安置鋼制擋圈(GB/T891-1986)，擋圈用緊定螺釘(GB/T68-2000)固定在螺桿端部。其中：1.5t=10.5mm D13=(1.71.9)d=1.8×40=72mm(1.41.6)d=1.5d=60mmH1+H=260+63=323mm0.25d=10mm1.6螺桿強度計算對受力較大的螺桿應根據(jù)第四強度理論校核螺桿的強度。強度計算方法參閱教材公式(6.23)，s其中扭矩=65×103tan(5.14°+3.5°) ×式中：y為螺紋中徑處升角，rv為當量摩擦

69、角。查手冊，45鋼，=355MPas=查手冊表3-8，d1=d-8=32mmT=180.25N·m=355Mpa故，=93.8s=88.8MPa1.7穩(wěn)定性計算細長的螺桿工作時受到較大的軸向壓力可能失穩(wěn)，為此應按穩(wěn)定性條件驗算螺桿的穩(wěn)定性。Fcr / F ³ 2.5 4螺桿的臨界載荷Fcr與柔度s有關(guān)，s=m l/i，m為螺桿的長度系數(shù)，與螺桿的端部結(jié)構(gòu)有關(guān)，l為舉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為螺桿危險截面的慣性半徑，若危險截面面積A=pd12/4，則(I為螺桿危險截面的軸慣性矩)當螺桿的柔度s40時，可以不必進行穩(wěn)定性校核。

70、計算時應注意正確確定。1.7.1計算柔度 （1）計算螺桿危險截面的軸慣性矩I和iI=（2）求起重物后托杯底面到螺母中部的高度llH+5p+(1.41.6)d =240+5×7+1.5×40(3) 計算柔度查教材，b取2(一端固定，一端自由)查手冊表1-6，E取200GPas=88.8MPaI=5.1×10-8m4i=8×10-3ml =335mmb=2s=m l/i=1.7.2穩(wěn)定性計算（1）計算臨界載荷Fcr Fcr=(2) 穩(wěn)定性計算2. 螺母設(shè)計與計算2.1選取螺母材料螺母材料一般可選用青銅，對于尺寸較大的螺母可采用鋼或鑄鐵制造，其內(nèi)孔澆注青銅或巴氏合金。此題選青銅2.2確定螺母