汽車轉(zhuǎn)向機(jī)構(gòu)模擬機(jī)械原理課程設(shè)計(jì)

1、一、工作原理汽車機(jī)械轉(zhuǎn)向系是由轉(zhuǎn)向操縱機(jī)構(gòu)、轉(zhuǎn)向器和轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)三大部分組成。根據(jù)轉(zhuǎn)向器位置和轉(zhuǎn)向輪懸架類型不同，轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的組成和布置分為與非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)和與獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)。這里討論的是與非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)。 轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)是將轉(zhuǎn)向器輸出的力和運(yùn)動(dòng)傳給轉(zhuǎn)向橋兩側(cè)的轉(zhuǎn)向節(jié)，使兩側(cè)轉(zhuǎn)向輪偏轉(zhuǎn)，并使兩轉(zhuǎn)向輪偏轉(zhuǎn)按一定的關(guān)系變化，以保證汽車轉(zhuǎn)向時(shí)車輪與地面的相對(duì)滑動(dòng)盡可能小。為了避免汽車轉(zhuǎn)向時(shí)產(chǎn)生的路面對(duì)汽車行駛的附加阻力和輪胎磨損太快，要求轉(zhuǎn)向系在汽車轉(zhuǎn)向時(shí)， 所有車輪均做純滾動(dòng)而不產(chǎn)生側(cè)向滑移，圖 1 中兩側(cè)車輪偏轉(zhuǎn)角 和 的理想關(guān)系為：cot =cot +B

2、/LB兩側(cè)主銷軸線與地面相交點(diǎn)之間的距離L汽車軸距因此轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)轉(zhuǎn)向梯形的幾何參數(shù)需要優(yōu)化確定，但是，至今所有的汽車的轉(zhuǎn)向梯形都只能設(shè)計(jì)得在一定的車輪偏轉(zhuǎn)角圍，接近于理想關(guān)系。為了模擬的方便，轉(zhuǎn)向機(jī)構(gòu)簡(jiǎn)化為圖5.1 所示，由車輪、等腰梯形機(jī)構(gòu)（包括左、右梯形臂、機(jī)架、轉(zhuǎn)向橫拉桿） 、轉(zhuǎn)向節(jié)臂、轉(zhuǎn)向直拉桿、方向盤等組成。圖 1（名詞解釋）非獨(dú)立懸架：非獨(dú)立懸架是相對(duì)與獨(dú)立懸架（individual wheel suspension）的車輪結(jié)構(gòu)。非獨(dú)立懸架的結(jié)構(gòu)特點(diǎn)是兩側(cè)車輪由一根整體式車架相連，車輪連同車橋一起通過彈性懸架懸掛在車架或車身的下面。非獨(dú)立懸架具有結(jié)構(gòu)簡(jiǎn)單、成本低、強(qiáng)度高、保養(yǎng)容易

3、、行車中前輪定位變化小的優(yōu)點(diǎn)，但由于其舒適性及操縱穩(wěn)定性都較差，在現(xiàn)代轎車中基本上已不再使用，多用在貨車和大客車上。非獨(dú)立懸架與獨(dú)立懸架的比較：二、四桿機(jī)構(gòu)的設(shè)計(jì)通過圖 1 我們可以知道， 非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)是一個(gè)絞接四桿機(jī)構(gòu)。汽車直線行駛時(shí)，我們不妨稱之為“原始位置”。為了使左右轉(zhuǎn)向有相同的性質(zhì)，這個(gè)四桿機(jī)構(gòu)在原始位置是必須為對(duì)稱機(jī)構(gòu)。又要滿足 cot =cot +B/L，只能是等腰梯形機(jī)構(gòu)。不難理解，車輪轉(zhuǎn)角即為梯形臂從原始位置繞機(jī)架轉(zhuǎn)動(dòng)的轉(zhuǎn)角。隨意選取一款可能使用非獨(dú)立懸架的汽車：解放牌 CA1091PK2LA95型平頭長(zhǎng)軸距載貨汽車前輪距 :1800 ( 毫米 )軸距 :43

4、60 ( 毫米 )輪胎規(guī)格 :9.00-20,8.25-201 英寸 = 2.539999918厘米 ( 公分 ) 。即： L=4360mm； B 近似等于 1800-9*2.539999918*10=1571.400mmB/L=0.360cot =cot +B/L滿足以上要求的一組值（汽車轉(zhuǎn)向輪的最大轉(zhuǎn)角通常為外輪2535°，輪 3545°）：外輪轉(zhuǎn)角最大值 =30°輪轉(zhuǎn)角最大值 =36.09 °一、設(shè)計(jì)在 Pro/E 的幫助下獲得一組合適且滿足要求的四桿機(jī)構(gòu)。由于設(shè)計(jì)者能力有限，不能設(shè)計(jì)一套絕對(duì)滿足cot =cot +B/L 的四桿機(jī)構(gòu)，只能設(shè)計(jì)達(dá)到

5、最大轉(zhuǎn)角時(shí)滿足cot =cot +B/L。得到示意圖：機(jī)架 L=1571.4連架桿 L1=200連桿 L2=1473.99連架桿即為梯形臂，連桿即為轉(zhuǎn)向橫拉桿。二、檢驗(yàn)在 Pro/E 中分別定外轉(zhuǎn)角 20°、10°，檢驗(yàn)轉(zhuǎn)角。如圖：制表： 角（外轉(zhuǎn)角） 角（轉(zhuǎn)角）理想值（度）實(shí)際值（度）理想值（度）實(shí)際值（度）101010.6610.50202022.7322.23303036.0936.09從上表中可以看出轉(zhuǎn)角的實(shí)際值與理想值偏差在一位小數(shù)，此設(shè)計(jì)方案可行。三、設(shè)計(jì)結(jié)果機(jī)架 L=1571.4連架桿 L1=200連桿 L2=1473.99 角（外轉(zhuǎn)角）最值30°三

6、、各構(gòu)件的設(shè)計(jì)及零件圖制作一、節(jié)臂（左梯形臂）完成二、梯形臂完成三、機(jī)架放大圖完成四、連桿完成四、裝配機(jī)構(gòu)一、裝配機(jī)架在 Pro/E 中新建組件文件。插入機(jī)架，選固定的約束二、裝配節(jié)臂插入節(jié)臂。選銷釘約束（A5與 A3）再選擇機(jī)架和節(jié)臂的兩斷面對(duì)齊。完成后為三、裝配梯形臂A4 與 A4銷釘連接再取端面對(duì)齊。完成后為四、裝配連桿插入連桿。 A4與 A3 銷釘連接再取兩斷面對(duì)齊。完成后得點(diǎn)右鍵添加集。 A3與 A6銷釘連接，同時(shí)斷面對(duì)齊。完成后為五、運(yùn)動(dòng)分析節(jié)臂與機(jī)架連接的銷釘處設(shè)置一個(gè)伺服電機(jī)，設(shè)置輪廓，規(guī)選“位置”，“?！边x常數(shù)“-75.91 ”，點(diǎn)確定。 打開分析定義， 運(yùn)行獲得汽車直行時(shí)傳

7、動(dòng)機(jī)構(gòu)位置，如圖重新編輯定義伺服電機(jī)，使其反向；設(shè)置輪廓，規(guī)選“速度”，“模”選常數(shù)“ 10”，點(diǎn)確定。打開分析定義，時(shí)間設(shè)置為3，這樣最大外轉(zhuǎn)角即為30 度。點(diǎn)運(yùn)行。運(yùn)行結(jié)果為左轉(zhuǎn)彎最大位置，如圖點(diǎn)擊測(cè)量結(jié)果。新建測(cè)量1，以節(jié)臂與連桿銷釘連接的軸線為測(cè)量點(diǎn)，類型選位置，評(píng)估方法選每個(gè)時(shí)間步長(zhǎng)。類似地新建測(cè)量2，唯一不同在于測(cè)量點(diǎn)選取梯形臂與連桿銷釘連接的軸線。分別出圖分別點(diǎn)文件選輸出Excel 。圖表如下圖角（外轉(zhuǎn)角）AnalysisDefinition2:measure1 (度)11.59012689-8.40987311100.511.522.533.5-28.40987311量測(cè) -4

8、8.40987311-68.40987311-88.40987311-108.4098731時(shí)間( 秒)角（轉(zhuǎn)角）AnalysisDefinition2:measure2 (度)82.3093467777.3093467772.3093467767.30934677量 62.30934677測(cè) 57.30934677 52.3093467747.3093467742.3093467737.3093467700.511.522.533.5時(shí)間( 秒)角的 Excel 復(fù)制到角 Excel 里，再加入理想值， 以方便對(duì)比。 結(jié)果如下表角（外轉(zhuǎn)角）角（轉(zhuǎn)角）時(shí)間理想轉(zhuǎn)時(shí)間測(cè)量理想值測(cè)量理想轉(zhuǎn)角理想值

9、(秒)角(秒)0-75.91030-75.91075.90033075.910.02-76.12350.2-76.110.0275.68710.20025275.709750.04-76.33680.4-76.310.0475.473290.4010080.06-76.550.6-76.510.0675.25910.602270.08-76.76330.8-76.710.0875.044510.8040410.1-76.97661-76.910.174.829531.0063220.12-77.18981.2-77.110.1274.614161.2091150.14-77.40311.4-7

10、7.310.1474.398391.4124220.16-77.61651.6-77.510.1674.182231.6162440.18-77.82981.8-77.710.1873.965671.8205830.2-78.04322-77.910.273.74872.0254420.22-78.25652.2-78.110.2273.531342.2308210.24-78.46992.4-78.310.2473.313572.4367230.26-78.68332.6-78.510.2673.095392.6431490.28-78.89672.8-78.710.2872.876812.

11、8501010.3-79.11023-78.910.372.657813.057580.32-79.32363.2-79.110.3272.438413.2655890.34-79.53713.4-79.310.3472.218593.4741280.36-79.75063.6-79.510.3671.998353.68320.38-79.96413.8-79.710.3871.77773.8928060.4-80.17774-79.910.471.556634.1029470.42-80.39124.2-80.110.4271.335134.3136250.44-80.60484.4-80.

12、310.4471.113214.5248410.46-80.81844.6-80.510.4670.890864.73659875.5089975.3077375.1059674.9036874.7008874.4975874.2937674.0894273.8845673.6791873.4732873.2668573.059972.8524272.6444172.4358772.226872.0171971.8070571.5963871.3851671.17340.48-81.0324.8-80.710.4870.668084.9488960.5-81.24575-80.910.570.

13、444875.1617360.52-81.45935.2-81.110.5270.221235.3751210.54-81.6735.4-81.310.5469.997155.5890520.56-81.88675.6-81.510.5669.772635.8035290.58-82.10055.8-81.710.5869.547676.0185550.6-82.31436-81.910.669.322266.234130.62-82.5286.2-82.110.6269.096416.4502560.64-82.74196.4-82.310.6468.870116.6669340.66-82

14、.95576.6-82.510.6668.643356.8841650.68-83.16966.8-82.710.6868.416147.101950.7-83.38357-82.910.768.188477.3202920.72-83.59747.2-83.110.7267.960347.5391890.74-83.81147.4-83.310.7467.731747.7586440.76-84.02547.6-83.510.7667.502677.9786580.78-84.23947.8-83.710.7867.273148.1992320.8-84.45348-83.910.867.0

15、43138.4203670.82-84.66758.2-84.110.8266.812648.6420630.84-84.88168.4-84.310.8466.581678.8643210.86-85.09588.6-84.510.8666.350229.0871430.88-85.30998.8-84.710.8866.118289.3105290.9-85.52419-84.910.965.885849.53448170.961170.7482670.5348870.3209570.1064769.8914569.6758769.4597469.2430769.0258468.80805

16、68.5897168.3708168.1513667.9313467.7107767.4896367.2679467.0456866.8228666.5994766.375520.92-85.73849.2-85.110.9265.652919.7589980.94-85.95279.4-85.310.9465.419499.9840810.96-86.1679.6-85.510.9665.1855610.209730.98-86.38139.8-85.710.9864.9511210.435951-86.595710-85.91164.7161710.662741.02-86.810210.

17、2-86.111.0264.4807110.890091.04-87.024610.4-86.311.0464.2447311.118021.06-87.239110.6-86.511.0664.0082211.346511.08-87.453710.8-86.711.0863.7711911.575581.1-87.668211-86.911.163.5336311.805221.12-87.882911.2-87.111.1263.2955212.035421.14-88.097511.4-87.311.1463.0568812.26621.16-88.312211.6-87.511.16

18、62.817712.497551.18-88.52711.8-87.711.1862.5779612.729481.2-88.741812-87.911.262.3376712.961971.22-88.956612.2-88.111.2262.0968213.195041.24-89.171512.4-88.311.2461.855413.428681.26-89.386412.6-88.511.2661.6134113.662891.28-89.601412.8-88.711.2861.3708513.897671.3-89.816413-88.911.361.127714.133031.

19、32-90.031513.2-89.111.3260.8839714.368961.34-90.246613.4-89.311.3460.6396514.6054666.15165.9259265.7002765.4740565.2472665.0199164.7919864.5634964.3344264.1047863.8745863.643863.4124563.1805262.9480362.7149662.4813262.2471162.0123361.7769761.5410461.304541.36-90.461813.6-89.511.3660.3947314.842531.3

20、8-90.67713.8-89.711.3860.1492115.080171.4-90.892314-89.911.459.9030715.318391.42-91.107714.2-90.111.4259.6563215.557171.44-91.32314.4-90.311.4459.4089515.796531.46-91.538514.6-90.511.4659.1609516.036451.48-91.75414.8-90.711.4858.9123216.276951.5-91.969515-90.911.558.6630416.518011.52-92.185115.2-91.

21、111.5258.4131216.759641.54-92.400815.4-91.311.5458.1625417.001841.56-92.616515.6-91.511.5657.911317.24461.58-92.832315.8-91.711.5857.6593917.487941.6-93.048216-91.911.657.406817.731831.62-93.264116.2-92.111.6257.1535317.976291.64-93.480116.4-92.311.6456.8995618.221311.66-93.696116.6-92.511.6656.6449

22、18.46691.68-93.912216.8-92.711.6856.3895318.713041.7-94.128417-92.911.756.1334418.959751.72-94.344617.2-93.111.7255.8766319.207011.74-94.56117.4-93.311.7455.6190819.454831.76-94.777317.6-93.511.7655.3607919.703211.78-94.993817.8-93.711.7855.1017519.9521461.0674760.8298360.5916160.3528360.1134759.873

23、5559.6330559.3919959.1503658.9081658.665458.4220658.1781757.9337157.6886957.443157.1969656.9502556.7029956.4551756.2067955.957861.8-95.210318-93.911.854.8419520.201621.82-95.426918.2-94.111.8254.5813820.451651.84-95.643618.4-94.311.8454.3200320.702241.86-95.860418.6-94.511.8654.0578920.953371.88-96.

24、077218.8-94.711.8853.7949521.205051.9-96.294119-94.911.953.531221.457271.92-96.511119.2-95.111.9253.2666321.710031.94-96.728219.4-95.311.9453.0012221.963341.96-96.945419.6-95.511.9652.7349822.217181.98-97.162719.8-95.711.9852.4678822.471562-97.3820-95.91252.1999122.726482.02-97.597420.2-96.112.0251.

25、9310622.981922.04-97.81520.4-96.312.0451.6613323.23792.06-98.032620.6-96.512.0651.3906923.49442.08-98.250320.8-96.712.0851.1191423.751432.1-98.468121-96.912.150.8466524.008992.12-98.68621.2-97.112.1250.5732224.267062.14-98.90421.4-97.312.1450.2988424.525652.16-99.122121.6-97.512.1650.0234824.784752.

26、18-99.340321.8-97.712.1849.7471425.044372.2-99.558722-97.912.249.4697925.30452.22-99.777122.2-98.112.2249.1914325.5651355.7083855.4583555.2077654.9566354.7049554.4527354.1999753.9466653.6928253.4384453.1835252.9280852.672152.415652.1585751.9010151.6429451.3843551.1252550.8656350.605550.344872.24-99.

27、995622.4-98.312.2448.9120425.826262.26-100.21422.6-98.512.2648.6315926.08792.28-100.43322.8-98.712.2848.3500826.350032.3-100.65223-98.912.348.0674826.612662.32-100.87123.2-99.112.3247.7837926.875782.34-101.0923.4-99.312.3447.4989727.139382.36-101.30923.6-99.512.3647.2130127.403472.38-101.52923.8-99.

28、712.3846.925927.668042.4-101.74824-99.912.446.637627.933092.42-101.96824.2-100.112.4246.3481128.198612.44-102.18824.4-100.312.4446.057428.46462.46-102.40724.6-100.512.4645.7654428.731052.48-102.62824.8-100.712.4845.4722228.997972.5-102.84825-100.912.545.1777129.265352.52-103.06825.2-101.112.5244.881

29、8929.533182.54-103.28925.4-101.312.5444.5847329.801462.56-103.50925.6-101.512.5644.2862130.070192.58-103.7325.8-101.712.5843.986330.339362.6-103.95126-101.912.643.6849730.608972.62-104.17226.2-102.112.6243.382230.879012.64-104.39326.4-102.312.6443.0779531.149482.66-104.61526.6-102.512.6642.772231.42

30、03750.0837449.822149.5599749.2973449.0342248.7706248.5065348.2419647.9769147.7113947.445447.1789546.9120346.6446546.3768246.1085445.8398145.5706445.3010345.0309944.7605244.489632.68-104.83626.8-102.712.6842.4649231.691692.7-105.05827-102.912.742.1560731.963422.72-105.2827.2-103.112.7241.8456232.2355

31、62.74-105.50227.4-103.312.7441.5335332.508112.76-105.72527.6-103.512.7641.2197732.781062.78-105.94727.8-103.712.7840.9043133.05442.8-106.1728-103.912.840.587133.328142.82-106.39328.2-104.112.8240.268133.602262.84-106.61628.4-104.312.8439.9472733.876772.86-106.8428.6-104.512.8639.6245834.151652.88-10

32、7.06328.8-104.712.8839.2999734.42692.9-107.28729-104.912.938.973434.702522.92-107.51129.2-105.112.9238.6448134.97852.94-107.73529.4-105.312.9438.3141735.254832.96-107.9629.6-105.512.9637.9814235.531522.98-108.18529.8-105.712.9837.6464935.808553-108.4130-105.91337.3093536.08591測(cè)量值與理想值聯(lián)合制成圖表，角與角分別為44.

33、2183143.9465843.6744443.4018943.1289442.855642.5818642.3077442.0332341.7583541.483141.2074840.931540.6551740.3784840.1014539.824090 061.-200-40角轉(zhuǎn)-60-80-100-12080706050角轉(zhuǎn) 40302010004812.0023.024.084.065.046.07.08.048.069.089.0角284662844628124. 7902. 578. . .1.2.1111122222時(shí)間角2644826148268412. 5689. 23

34、56. 9. .1.2.2 .11111122222時(shí)間測(cè)量理想值測(cè)量理想值由于節(jié)臂勻速轉(zhuǎn)動(dòng)， 所以上面兩表中的橫坐標(biāo)也可看作是汽車的轉(zhuǎn)角。隨著汽車轉(zhuǎn)角的增大，實(shí)際值與理想值的偏差增大。 角與角的最大偏差分別2.5 °和 2.53155 °。偏差的產(chǎn)生， 設(shè)計(jì)的優(yōu)化不夠是主要原因。此外，所用到的方法和手段也是產(chǎn)生偏差的原因。 比如，四連桿的設(shè)計(jì)時(shí)得出的連桿長(zhǎng)1473.99 是 Pro/E 自動(dòng)省去后面的數(shù)得出的近似值。再如，輪轉(zhuǎn)角最大值=36.09 °也是取的近似值，而設(shè)計(jì)四連桿時(shí)利用了這個(gè)值，更精確的值是36.08591 °。需要注意的是，近似值的影響可能使偏差增大也可能使之減小，是不可知的。六、總結(jié)在此次設(shè)計(jì)過程中， 我深刻體會(huì)到數(shù)學(xué)功底對(duì)工程設(shè)計(jì)的重要性。要成為一流的工程設(shè)計(jì)師，掌握高級(jí)數(shù)學(xué)知識(shí)和能力是必不可少的。在教材汽車設(shè)計(jì)里面，非獨(dú)立懸架配用的轉(zhuǎn)向傳動(dòng)機(jī)構(gòu)的設(shè)計(jì)，運(yùn)用數(shù)學(xué)方法獲得優(yōu)化的設(shè)計(jì)結(jié)果。而我卻很難看懂，我的設(shè)計(jì)也就沒有了這么好的參考。同時(shí)我也認(rèn)識(shí)到，路不只有一條，我們可以在計(jì)算機(jī)的幫助下， 解決一些被自己數(shù)學(xué)能力限制而不能完成的工作。隨著工程輔助軟件的不斷發(fā)展，計(jì)算機(jī)解決工程問題的能力不斷強(qiáng)大，但是我想，學(xué)習(xí)高級(jí)數(shù)學(xué)、提