拖拉機的工作原理及基本組成

一、拖拉機的工作原理

(一)輪式拖拉機的工作原理

1、拖拉機的行駛

拖(tuo)拉(la)(la)機(ji)能(neng)行(xing)(xing)駛(shi)(shi)(shi)是靠(kao)內燃機(ji)的動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)經傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)系統(tong)，使驅動(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)獲(huo)得驅動(dong)(dong)(dong)(dong)(dong)(dong)扭矩(ju)Ｍk，獲(huo)得驅動(dong)(dong)(dong)(dong)(dong)(dong)扭矩(ju)的驅動(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)再通過輪(lun)(lun)胎花(hua)紋和(he)(he)輪(lun)(lun)胎表(biao)面(mian)給(gei)地(di)面(mian)小(xiao)(xiao)、向(xiang)后的水平(ping)作(zuo)(zuo)用(yong)力(li)(li)(li)(li)(切線(xian)力(li)(li)(li)(li))，而(er)地(di)面(mian)對驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)大(da)小(xiao)(xiao)相(xiang)等、方(fang)向(xiang)相(xiang)反的水平(ping)飯(fan)(fan)作(zuo)(zuo)用(yong)力(li)(li)(li)(li)Pk，這個Pk飯(fan)(fan)作(zuo)(zuo)用(yong)力(li)(li)(li)(li)就是推動(dong)(dong)(dong)(dong)(dong)(dong)拖(tuo)拉(la)(la)機(ji)向(xiang)前(qian)行(xing)(xing)駛(shi)(shi)(shi)的驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)(也稱喂推進力(li)(li)(li)(li))。當驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)Pk足以克服前(qian)后車(che)輪(lun)(lun)向(xiang)前(qian)滾動(dong)(dong)(dong)(dong)(dong)(dong)阻力(li)(li)(li)(li)和(he)(he)所帶農具的牽引阻力(li)(li)(li)(li)時(shi)，拖(tuo)拉(la)(la)機(ji)便向(xiang)前(qian)行(xing)(xing)駛(shi)(shi)(shi)。若(ruo)將(jiang)驅動(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)支離地(di)面(mian)，即驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)Pk等于(yu)零(ling)，則驅動(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)只能(neng)原(yuan)地(di)空轉，拖(tuo)拉(la)(la)機(ji)不能(neng)行(xing)(xing)駛(shi)(shi)(shi)；若(ruo)滾動(dong)(dong)(dong)(dong)(dong)(dong)阻力(li)(li)(li)(li)與牽引阻力(li)(li)(li)(li)之和(he)(he)大(da)于(yu)驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)Ｐk時(shi)，拖(tuo)拉(la)(la)機(ji)也不能(neng)行(xing)(xing)駛(shi)(shi)(shi)。由此可見輪(lun)(lun)式拖(tuo)拉(la)(la)機(ji)行(xing)(xing)駛(shi)(shi)(shi)是由驅動(dong)(dong)(dong)(dong)(dong)(dong)扭矩(ju)驅動(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)與地(di)面(mian)間的相(xiang)互作(zuo)(zuo)用(yong)而(er)實現的，并且驅動(dong)(dong)(dong)(dong)(dong)(dong)力(li)(li)(li)(li)要大(da)于(yu)滾動(dong)(dong)(dong)(dong)(dong)(dong)阻力(li)(li)(li)(li)與牽引阻力(li)(li)(li)(li)之和(he)(he)。下面(mian)我(wo)們再分析(xi)一下影(ying)響拖(tuo)拉(la)(la)機(ji)行(xing)(xing)駛(shi)(shi)(shi)有主要因素。

2、影響拖拉機行駛的主要因素

(1)滾動阻力

拖(tuo)(tuo)拉(la)機(ji)(ji)的(de)(de)(de)滾(gun)(gun)動(dong)(dong)阻(zu)力(li)，主(zhu)要是(shi)由于(yu)輪(lun)(lun)(lun)(lun)(lun)胎和(he)土(tu)(tu)壤(rang)的(de)(de)(de)變(bian)(bian)(bian)形(xing)而產生的(de)(de)(de)，在(zai)(zai)(zai)(zai)拖(tuo)(tuo)拉(la)機(ji)(ji)的(de)(de)(de)重量(liang)作(zuo)用(yong)(yong)下(xia)(xia)，輪(lun)(lun)(lun)(lun)(lun)胎被壓(ya)(ya)扁(bian)、土(tu)(tu)壤(rang)被壓(ya)(ya)實。車輪(lun)(lun)(lun)(lun)(lun)在(zai)(zai)(zai)(zai)滾(gun)(gun)動(dong)(dong)過程中(zhong)(zhong)、輪(lun)(lun)(lun)(lun)(lun)胎沿圓周圍方向(xiang)與(yu)地(di)(di)(di)面(mian)(mian)(mian)相(xiang)接觸的(de)(de)(de)各個(ge)部上繼被壓(ya)(ya)扁(bian)變(bian)(bian)(bian)形(xing)，且把(ba)車輪(lun)(lun)(lun)(lun)(lun)前面(mian)(mian)(mian)高出土(tu)(tu)壤(rang)壓(ya)(ya)下(xia)(xia)去使土(tu)(tu)壤(rang)壓(ya)(ya)下(xia)(xia)去使土(tu)(tu)壤(rang)變(bian)(bian)(bian)形(xing)而形(xing)成輪(lun)(lun)(lun)(lun)(lun)轍，即產生了阻(zu)礙(ai)車輪(lun)(lun)(lun)(lun)(lun)向(xiang)前滾(gun)(gun)動(dong)(dong)的(de)(de)(de)滾(gun)(gun)動(dong)(dong)阻(zu)力(li)。影響滾(gun)(gun)動(dong)(dong)阻(zu)力(li)的(de)(de)(de)因(yin)(yin)(yin)素(su)很多，主(zhu)要與(yu)地(di)(di)(di)面(mian)(mian)(mian)的(de)(de)(de)堅實和(he)潮濕(shi)程度上的(de)(de)(de)垂(chui)直載荷(he)的(de)(de)(de)大(da)小等因(yin)(yin)(yin)素(su)有關(guan)。對同(tong)一臺拖(tuo)(tuo)拉(la)機(ji)(ji)來說，若地(di)(di)(di)面(mian)(mian)(mian)條(tiao)件(jian)不同(tong)，其滾(gun)(gun)動(dong)(dong)阻(zu)力(li)也(ye)(ye)不同(tong)，如在(zai)(zai)(zai)(zai)瀝青和(he)水(shui)泥(ni)或干硬地(di)(di)(di)面(mian)(mian)(mian)上行駛滾(gun)(gun)動(dong)(dong)阻(zu)力(li)小，拖(tuo)(tuo)拉(la)機(ji)(ji)牽引力(li)就(jiu)大(da)，在(zai)(zai)(zai)(zai)同(tong)樣使用(yong)(yong)條(tiao)件(jian)下(xia)(xia)，若加(jia)(jia)在(zai)(zai)(zai)(zai)輪(lun)(lun)(lun)(lun)(lun)胎上的(de)(de)(de)重量(liang)越(yue)大(da)，土(tu)(tu)壤(rang)在(zai)(zai)(zai)(zai)垂(chui)直方向(xiang)的(de)(de)(de)變(bian)(bian)(bian)形(xing)越(yue)大(da)，滾(gun)(gun)動(dong)(dong)阻(zu)力(li)也(ye)(ye)就(jiu)越(yue)大(da)。一般說來，減(jian)(jian)少輪(lun)(lun)(lun)(lun)(lun)胎本身的(de)(de)(de)變(bian)(bian)(bian)形(xing)和(he)土(tu)(tu)壤(rang)垂(chui)直方向(xiang)的(de)(de)(de)變(bian)(bian)(bian)形(xing)，有利于(yu)減(jian)(jian)少滾(gun)(gun)動(dong)(dong)阻(zu)力(li)。若拖(tuo)(tuo)拉(la)機(ji)(ji)在(zai)(zai)(zai)(zai)松軟(ruan)(ruan)地(di)(di)(di)面(mian)(mian)(mian)上行駛，采(cai)(cai)用(yong)(yong)低壓(ya)(ya)輪(lun)(lun)(lun)(lun)(lun)胎，加(jia)(jia)大(da)輪(lun)(lun)(lun)(lun)(lun)胎支承面(mian)(mian)(mian)積，則可減(jian)(jian)小土(tu)(tu)壤(rang)在(zai)(zai)(zai)(zai)垂(chui)直方向(xiang)的(de)(de)(de)變(bian)(bian)(bian)形(xing)，降低滾(gun)(gun)動(dong)(dong)阻(zu)力(li)，從而提(ti)高牽引力(li)。由于(yu)拖(tuo)(tuo)拉(la)機(ji)(ji)主(zhu)要用(yong)(yong)于(yu)田(tian)間(jian)作(zuo)業，多在(zai)(zai)(zai)(zai)松軟(ruan)(ruan)地(di)(di)(di)面(mian)(mian)(mian)上行駛，為減(jian)(jian)小土(tu)(tu)壤(rang)在(zai)(zai)(zai)(zai)垂(chui)直方向(xiang)的(de)(de)(de)變(bian)(bian)(bian)形(xing)，因(yin)(yin)(yin)此(ci)拖(tuo)(tuo)拉(la)機(ji)(ji)一般采(cai)(cai)用(yong)(yong)的(de)(de)(de)最(zui)低壓(ya)(ya)輪(lun)(lun)(lun)(lun)(lun)胎，采(cai)(cai)用(yong)(yong)加(jia)(jia)寬輪(lun)(lun)(lun)(lun)(lun)胎也(ye)(ye)是(shi)同(tong)樣的(de)(de)(de)道理。在(zai)(zai)(zai)(zai)我們經營中(zhong)(zhong)應注意低壓(ya)(ya)輪(lun)(lun)(lun)(lun)(lun)胎、加(jia)(jia)寬輪(lun)(lun)(lun)(lun)(lun)胎和(he)高壓(ya)(ya)輪(lun)(lun)(lun)(lun)(lun)胎在(zai)(zai)(zai)(zai)使用(yong)(yong)上的(de)(de)(de)區別。

(2)牽引阻力

牽(qian)引阻(zu)力是(shi)拖(tuo)拉(la)機(ji)帶動(dong)農機(ji)具(ju)進行作業所要克服的阻(zu)力，它等(deng)于拖(tuo)拉(la)機(ji)通過連接(jie)裝置傳給農機(ji)具(ju)的牽(qian)引力。由于牽(qian)引力等(deng)于驅(qu)動(dong)減(jian)去滾動(dong)阻(zu)力，因此，增加驅(qu)動(dong)力和減(jian)少滾動(dong)阻(zu)力是(shi)提(ti)高牽(qian)引力的有效措施。

(3)驅動力

它是(shi)路面對驅(qu)(qu)(qu)(qu)動(dong)(dong)輪(lun)的(de)(de)水平反(fan)作(zuo)用(yong)力(li)。因(yin)此，內燃機(ji)通過傳動(dong)(dong)系(xi)統傳到(dao)驅(qu)(qu)(qu)(qu)動(dong)(dong)輪(lun)上(shang)的(de)(de)驅(qu)(qu)(qu)(qu)動(dong)(dong)扭矩Ｍk的(de)(de)大小，表明了(le)拖拉(la)機(ji)的(de)(de)驅(qu)(qu)(qu)(qu)動(dong)(dong)力(li)Ｐk也(ye)越大。但(dan)由于(yu)Ｍk是(shi)由內燃機(ji)的(de)(de)功率決定的(de)(de)，因(yin)此Ｐk也(ye)受到(dao)內燃機(ji)功率的(de)(de)限(xian)制。同時(shi)Ｐk又受土壤(rang)(rang)條件的(de)(de)限(xian)制，不能無限(xian)增加，因(yin)為(wei)當土壤(rang)(rang)的(de)(de)反(fan)作(zuo)用(yong)力(li)即驅(qu)(qu)(qu)(qu)動(dong)(dong)力(li)Ｐk增加到(dao)一定程度時(shi)同，土壤(rang)(rang)被破壞，驅(qu)(qu)(qu)(qu)動(dong)(dong)輪(lun)嚴重打滑，驅(qu)(qu)(qu)(qu)動(dong)(dong)力(li)Ｐk不能再(zai)增加了(le)。我(wo)們(men)把土壤(rang)(rang)對驅(qu)(qu)(qu)(qu)動(dong)(dong)輪(lun)所能產生的(de)(de)最(zui)(zui)大反(fan)作(zuo)用(yong)力(li)叫做“附著(zhu)力(li)”。由此可見，驅(qu)(qu)(qu)(qu)動(dong)(dong)力(li)Ｐk的(de)(de)最(zui)(zui)大值除了(le)受內燃機(ji)率限(xian)制外，還受土壤(rang)(rang)附著(zhu)力(li)的(de)(de)限(xian)制，而(er)不能無限(xian)增加國。

附(fu)(fu)著(zhu)力(li)(li)(li)反映(ying)了驅(qu)動與土壤間(jian)產生最(zui)大(da)(da)驅(qu)動力(li)(li)(li)的(de)(de)能(neng)力(li)(li)(li)。影(ying)響附(fu)(fu)著(zhu)力(li)(li)(li)的(de)(de)因素很多，主要(yao)與地面的(de)(de)條(tiao)(tiao)(tiao)件，輪胎(tai)(tai)(tai)氣壓(ya)、尺寸、花紋和作用(yong)在(zai)(zai)(zai)輪胎(tai)(tai)(tai)上的(de)(de)垂直(zhi)載荷(he)的(de)(de)大(da)(da)小(xiao)等因素有關。對(dui)拖(tuo)拉(la)機(ji)來說，在(zai)(zai)(zai)一定的(de)(de)土壤條(tiao)(tiao)(tiao)件下(xia)，在(zai)(zai)(zai)一定的(de)(de)范圍內降(jiang)低輪胎(tai)(tai)(tai)氣壓(ya)、增(zeng)大(da)(da)輪胎(tai)(tai)(tai)支承(cheng)面積、改(gai)善(shan)車(che)輪對(dui)土壤的(de)(de)抓著(zhu)能(neng)力(li)(li)(li)、增(zeng)加(jia)車(che)輪的(de)(de)附(fu)(fu)著(zhu)重量等，都(dou)有利于(yu)提高(gao)拖(tuo)拉(la)機(ji)的(de)(de)附(fu)(fu)著(zhu)力(li)(li)(li)，在(zai)(zai)(zai)拖(tuo)拉(la)機(ji)上普遍(bian)采(cai)用(yong)低壓(ya)輪胎(tai)(tai)(tai)，有的(de)(de)拖(tuo)拉(la)機(ji)采(cai)用(yong)了加(jia)寬輪胎(tai)(tai)(tai)和高(gao)花紋輪胎(tai)(tai)(tai)以及在(zai)(zai)(zai)拖(tuo)拉(la)機(ji)驅(qu)動輪上加(jia)配(pei)重鐵，都(dou)是(shi)為了增(zeng)加(jia)拖(tuo)拉(la)機(ji)的(de)(de)附(fu)(fu)著(zhu)力(li)(li)(li)，提高(gao)拖(tuo)拉(la)機(ji)的(de)(de)牽引能(neng)力(li)(li)(li)而采(cai)取的(de)(de)措(cuo)施(shi)。但應指出驅(qu)動輪上加(jia)配(pei)重鐵，雖然可增(zeng)加(jia)附(fu)(fu)著(zhu)力(li)(li)(li)，但同時也增(zeng)加(jia)了土壤在(zai)(zai)(zai)垂直(zhi)方向(xiang)上的(de)(de)變形，增(zeng)加(jia)了滾動阻力(li)(li)(li)，因此是(shi)否加(jia)配(pei)重鐵，還要(yao)視(shi)具體使用(yong)條(tiao)(tiao)(tiao)件，權衡總(zong)的(de)(de)效果進行取舍。

拖(tuo)拉(la)機(ji)(ji)驅(qu)(qu)動(dong)輪(lun)與地面間產生的最大附(fu)(fu)著能(neng)(neng)(neng)(neng)力(li)(li)和(he)抵抗打(da)(da)滑(hua)(hua)(hua)的能(neng)(neng)(neng)(neng)力(li)(li)，稱為拖(tuo)拉(la)機(ji)(ji)的附(fu)(fu)著性(xing)能(neng)(neng)(neng)(neng)。若附(fu)(fu)著性(xing)能(neng)(neng)(neng)(neng)好(hao)，打(da)(da)滑(hua)(hua)(hua)較輕，則(ze)驅(qu)(qu)動(dong)扭(niu)矩就(jiu)(jiu)能(neng)(neng)(neng)(neng)充分(fen)利用(yong)，內燃機(ji)(ji)的能(neng)(neng)(neng)(neng)力(li)(li)也能(neng)(neng)(neng)(neng)得到充分(fen)的發(fa)揮，拖(tuo)拉(la)機(ji)(ji)在工作(zuo)時(shi)就(jiu)(jiu)顯(xian)得有勁(jing)。若附(fu)(fu)著性(xing)能(neng)(neng)(neng)(neng)差，打(da)(da)滑(hua)(hua)(hua)嚴重，則(ze)驅(qu)(qu)動(dong)扭(niu)矩就(jiu)(jiu)不能(neng)(neng)(neng)(neng)充分(fen)利用(yong)，內燃機(ji)(ji)的能(neng)(neng)(neng)(neng)力(li)(li)就(jiu)(jiu)不能(neng)(neng)(neng)(neng)得到充分(fen)的發(fa)揮，拖(tuo)拉(la)機(ji)(ji)在工作(zuo)時(shi)就(jiu)(jiu)顯(xian)得有勁(jing)使不出來，或者說拖(tuo)拉(la)機(ji)(ji)沒有多大勁(jing)。驅(qu)(qu)動(dong)輪(lun)嚴重打(da)(da)滑(hua)(hua)(hua)，會使拖(tuo)拉(la)機(ji)(ji)行駛速度降低，生產和(he)經(jing)濟性(xing)下降，同(tong)時(shi)也加(jia)快(kuai)了驅(qu)(qu)動(dong)輪(lun)輪(lun)胎的磨損，此外土壤的結構也會遭到破(po)壞。

(二)履帶式拖拉機的工作原理

履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)式(shi)(shi)(shi)與(yu)(yu)輪(lun)(lun)式(shi)(shi)(shi)拖(tuo)拉(la)(la)機(ji)(ji)不同，它是(shi)通過(guo)一條(tiao)卷(juan)繞(rao)的(de)(de)(de)(de)環形履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)支承在(zai)(zai)地(di)面(mian)上(shang)。履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)接(jie)(jie)(jie)(jie)觸(chu)地(di)面(mian)，履(lv)(lv)(lv)刺插入土內，驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)工不接(jie)(jie)(jie)(jie)地(di)。驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)在(zai)(zai)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)扭矩(ju)(ju)的(de)(de)(de)(de)作用(yong)(yong)(yong)下，通過(guo)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)上(shang)的(de)(de)(de)(de)輪(lun)(lun)齒和(he)履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)板(ban)節(jie)(jie)銷(xiao)之(zhi)間的(de)(de)(de)(de)嚙合(he)連續不斷地(di)把履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)從后(hou)方卷(juan)起。接(jie)(jie)(jie)(jie)地(di)那(nei)部分履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)給(gei)地(di)面(mian)一個(ge)(ge)向(xiang)后(hou)的(de)(de)(de)(de)作用(yong)(yong)(yong)力(li)，而需也相(xiang)應地(di)給(gei)履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)一個(ge)(ge)前的(de)(de)(de)(de)反(fan)作用(yong)(yong)(yong)力(li)Ｐk，這個(ge)(ge)Ｐk反(fan)作用(yong)(yong)(yong)是(shi)推動(dong)(dong)(dong)(dong)(dong)(dong)(dong)拖(tuo)拉(la)(la)機(ji)(ji)向(xiang)前行(xing)駛的(de)(de)(de)(de)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)力(li)。輪(lun)(lun)式(shi)(shi)(shi)拖(tuo)拉(la)(la)機(ji)(ji)的(de)(de)(de)(de)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)力(li)是(shi)直(zhi)接(jie)(jie)(jie)(jie)傳給(gei)行(xing)走輪(lun)(lun)的(de)(de)(de)(de)，而履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)式(shi)(shi)(shi)拖(tuo)拉(la)(la)機(ji)(ji)不同，它的(de)(de)(de)(de)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)力(li)Ｐk是(shi)通過(guo)卷(juan)繞(rao)在(zai)(zai)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)上(shang)的(de)(de)(de)(de)履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)傳給(gei)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)的(de)(de)(de)(de)輪(lun)(lun)軸(zhou)(zhou)，再由(you)(you)輪(lun)(lun)軸(zhou)(zhou)通過(guo)拖(tuo)拉(la)(la)機(ji)(ji)的(de)(de)(de)(de)機(ji)(ji)體(ti)傳到驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)上(shang)。當驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)力(li)足以(yi)克(ke)服滾(gun)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)阻力(li)和(he)所帶(dai)(dai)(dai)(dai)農具的(de)(de)(de)(de)牽引阻力(li)時，支重(zhong)輪(lun)(lun)就(jiu)在(zai)(zai)履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)上(shang)表面(mian)向(xiang)前滾(gun)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)，從而使拖(tuo)拉(la)(la)機(ji)(ji)向(xiang)前行(xing)駛。由(you)(you)于驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)不斷地(di)把履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)一節(jie)(jie)一節(jie)(jie)卷(juan)送到前方，再經導向(xiang)輪(lun)(lun)將其鋪在(zai)(zai)地(di)面(mian)上(shang)，因此支重(zhong)輪(lun)(lun)就(jiu)可連續地(di)在(zai)(zai)用(yong)(yong)(yong)履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)鋪設的(de)(de)(de)(de)軌道上(shang)滾(gun)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)了。由(you)(you)此可知，履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)式(shi)(shi)(shi)拖(tuo)拉(la)(la)機(ji)(ji)行(xing)使是(shi)由(you)(you)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)扭矩(ju)(ju)通過(guo)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)輪(lun)(lun)使履(lv)(lv)(lv)帶(dai)(dai)(dai)(dai)與(yu)(yu)地(di)面(mian)間的(de)(de)(de)(de)相(xiang)互作用(yong)(yong)(yong)而實現的(de)(de)(de)(de)，并且驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)力(li)大于滾(gun)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)阻力(li)與(yu)(yu)牽引阻力(li)之(zhi)和(he)。

驅動力(li)(li)的(de)(de)(de)最大值與輪式拖(tuo)拉機(ji)一(yi)(yi)(yi)樣，它一(yi)(yi)(yi)方面取決于內燃(ran)機(ji)的(de)(de)(de)能力(li)(li)，另一(yi)(yi)(yi)方面又(you)受到履(lv)帶(dai)與地面間附(fu)著(zhu)條件的(de)(de)(de)限(xian)制。一(yi)(yi)(yi)般說來，拖(tuo)拉機(ji)的(de)(de)(de)功率(lv)越(yue)大，驅動力(li)(li)就(jiu)越(yue)大。影響附(fu)著(zhu)力(li)(li)的(de)(de)(de)因素很多，就(jiu)其(qi)拖(tuo)拉機(ji)本身的(de)(de)(de)結(jie)構來說，合理的(de)(de)(de)選擇履(lv)刺(ci)、履(lv)帶(dai)的(de)(de)(de)形狀尺寸，在一(yi)(yi)(yi)定限(xian)度(du)內增(zeng)加履(lv)帶(dai)的(de)(de)(de)承受重量(liang)等，均可(ke)提高附(fu)著(zhu)力(li)(li)，增(zeng)加拖(tuo)拉機(ji)的(de)(de)(de)牽引力(li)(li)。

履帶式拖拉(la)機的(de)滾(gun)動阻力(li)是由土壤(rang)在垂直方向上(shang)的(de)變(bian)形和行走系各機件間的(de)相互摩(mo)擦作用而形成的(de)，減小滾(gun)動阻力(li)，可增加拖拉(la)機的(de)牽引力(li)。

二、拖拉機的基本組成

拖拉機雖是一(yi)種比較復雜(za)的機器(qi)，其型式和(he)大小也各不相同，但它們都是由(you)發動機、底盤和(he)電器(qi)設備三大部分組成的。

(一)發動機

它是(shi)拖拉機(ji)產(chan)生動力的裝置，其(qi)作用(yong)是(shi)將燃料(liao)的熱能轉變(bian)為機(ji)械能向外(wai)輸出動力。我(wo)國目前(qian)生產(chan)的農用(yong)拖拉機(ji)都采用(yong)柴油(you)機(ji)。

(二)底盤

它(ta)是(shi)(shi)拖(tuo)拉(la)(la)(la)機傳(chuan)遞(di)動(dong)(dong)(dong)(dong)(dong)力的(de)裝(zhuang)(zhuang)置。其(qi)作(zuo)用(yong)(yong)是(shi)(shi)將發動(dong)(dong)(dong)(dong)(dong)機的(de)動(dong)(dong)(dong)(dong)(dong)力傳(chuan)遞(di)給驅動(dong)(dong)(dong)(dong)(dong)輪和(he)工(gong)(gong)作(zuo)裝(zhuang)(zhuang)置使拖(tuo)拉(la)(la)(la)機行(xing)駛，并完成移動(dong)(dong)(dong)(dong)(dong)作(zuo)業(ye)或(huo)固(gu)定作(zuo)用(yong)(yong)。這個作(zuo)用(yong)(yong)是(shi)(shi)通(tong)過傳(chuan)動(dong)(dong)(dong)(dong)(dong)系(xi)(xi)統(tong)(tong)、行(xing)走系(xi)(xi)統(tong)(tong)、轉向系(xi)(xi)統(tong)(tong)、制動(dong)(dong)(dong)(dong)(dong)系(xi)(xi)統(tong)(tong)和(he)工(gong)(gong)作(zuo)裝(zhuang)(zhuang)置的(de)相互(hu)配合、協調工(gong)(gong)作(zuo)來實現(xian)的(de)，同(tong)時(shi)它(ta)們(men)又(you)構成了拖(tuo)拉(la)(la)(la)機的(de)骨(gu)架和(he)身軀(qu)。因此，我(wo)們(men)把上述的(de)四大系(xi)(xi)統(tong)(tong)和(he)一(yi)大裝(zhuang)(zhuang)置統(tong)(tong)稱為底盤。也就是(shi)(shi)說，在拖(tuo)拉(la)(la)(la)機的(de)整體中，除發動(dong)(dong)(dong)(dong)(dong)機和(he)電器設備以外的(de)所有其(qi)他系(xi)(xi)統(tong)(tong)和(he)裝(zhuang)(zhuang)置，統(tong)(tong)稱為拖(tuo)拉(la)(la)(la)機底盤。

(三)電器設備

它是保證拖拉機用電的裝置。其作用是解決照明、安全信號和發動機的起動。