一、四輪驅動是什么意思

四輪驅動，又稱全輪驅動，是指汽車前后輪都有動力的一種汽車驅動形式，一般用4X4或4WD來表示，如果你看見一輛車上標有上述字樣，那就表示該車輛擁有4輪驅動的功能，屬于四驅車。

四輪驅(qu)動可按(an)行駛路面狀態不同，將發動機(ji)輸出扭矩按(an)不同比例分布在前后所(suo)有的(de)輪子上，以提(ti)高(gao)汽車的(de)行駛能(neng)力，因此具(ju)有良好的(de)通過性能(neng)。

現如今很多汽(qi)車品(pin)牌都有四輪驅動汽(qi)車車型，其中又可(ke)分為(wei)全(quan)時驅動（Full－Time）、兼時驅動（Part-Time）、適時驅動（Real－Time）和(he)兼時/適時混(hun)和(he)驅動四種驅動模式(shi)。

二、四輪驅動系統的結構原理

四(si)輪驅動(dong)(dong)(dong)汽車(che)的傳動(dong)(dong)(dong)系統由離合器、變速(su)器、傳動(dong)(dong)(dong)軸、分動(dong)(dong)(dong)箱、前(qian)萬向(xiang)(xiang)傳動(dong)(dong)(dong)裝(zhuang)置(zhi)、前(qian)驅動(dong)(dong)(dong)橋、后(hou)萬向(xiang)(xiang)傳動(dong)(dong)(dong)裝(zhuang)置(zhi)和后(hou)驅動(dong)(dong)(dong)橋組成(cheng)。

工(gong)作時(shi)，分(fen)動(dong)(dong)(dong)(dong)(dong)器用來分(fen)配(pei)傳(chuan)(chuan)遞(di)到(dao)前(qian)軸(zhou)和后軸(zhou)的(de)轉(zhuan)矩(ju)，?鏈(lian)(lian)條(tiao)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)(dong)裝置將轉(zhuan)矩(ju)傳(chuan)(chuan)輸(shu)到(dao)前(qian)橋(qiao)，差速器通過與輸(shu)入軸(zhou)同軸(zhou)布置的(de)輸(shu)出軸(zhou)來驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)后橋(qiao)。前(qian)橋(qiao)轉(zhuan)矩(ju)傳(chuan)(chuan)輸(shu)到(dao)上(shang)鏈(lian)(lian)輪上(shang)。鏈(lian)(lian)輪位于上(shang)輸(shu)出軸(zhou)上(shang)，可自由(you)轉(zhuan)動(dong)(dong)(dong)(dong)(dong)，它通過鏈(lian)(lian)條(tiao)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)下(xia)鏈(lian)(lian)輪。下(xia)鏈(lian)(lian)輪與法蘭軸(zhou)固定在一(yi)起，形成前(qian)橋(qiao)主(zhu)減(jian)速器的(de)驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)力，驅(qu)(qu)動(dong)(dong)(dong)(dong)(dong)汽車。

三、四輪驅動系統的結構特點

四驅車的四(si)輪(lun)(lun)(lun)驅(qu)動(dong)(dong)裝(zhuang)置(zhi)是常嚙(nie)合(he)式(shi)，增加了(le)粘性耦合(he)器(qi)，省去了(le)手動(dong)(dong)分(fen)力器(qi)，自動(dong)(dong)將(jiang)(jiang)扭矩(ju)按(an)需分(fen)配(pei)在前后(hou)輪(lun)(lun)(lun)子上(shang)(shang)。在正(zheng)常路(lu)面(mian)上(shang)(shang)，四(si)輪(lun)(lun)(lun)驅(qu)動(dong)(dong)裝(zhuang)置(zhi)將(jiang)(jiang)引擎(qing)輸出(chu)(chu)扭矩(ju)的92%分(fen)配(pei)到前輪(lun)(lun)(lun)，8%分(fen)配(pei)到后(hou)輪(lun)(lun)(lun)；在滑溜(liu)的路(lu)面(mian)上(shang)(shang)，將(jiang)(jiang)至少40%的引擎(qing)機輸出(chu)(chu)扭矩(ju)分(fen)配(pei)給后(hou)輪(lun)(lun)(lun)；當前輪(lun)(lun)(lun)開始打滑時(shi)，前、后(hou)輪(lun)(lun)(lun)的轉速差異會使(shi)耦合(he)器(qi)中(zhong)的粘液立即變稠(chou)并鎖住耦合(he)器(qi)，從(cong)而(er)使(shi)傳動(dong)(dong)軸只將(jiang)(jiang)扭矩(ju)傳遞至后(hou)輪(lun)(lun)(lun)，待前、后(hou)輪(lun)(lun)(lun)地(di)轉速差異消(xiao)失就自動(dong)(dong)回復原有驅(qu)動(dong)(dong)形式(shi)。