潤滑油低溫流(liu)動(dong)性指標之(zhi)一：粘度

在機械正常工作的(de)溫度(du)下，潤滑(hua)油(you)(you)粘度(du)對(dui)流(liu)動性的(de)影響主要(yao)體現在機械的(de)散熱(re)效果，這一問(wen)題，巳(si)由機械設(she)計和潤滑(hua)油(you)(you)粘度(du)的(de)選擇(ze)而解決，因而，對(dui)潤滑(hua)油(you)(you)流(liu)動性所考慮(lv)的(de)主要(yao)問(wen)題是低(di)溫下潤滑(hua)油(you)(you)粘度(du)增大后對(dui)其性能和機械工作造成的(de)影響。

    1.粘度(du)增(zeng)大時(shi)磨損的(de)形響(xiang)

    潤滑油(you)(you)的(de)(de)(de)流動(dong)性主要是(shi)在低溫(wen)下不(bu)易達(da)到機(ji)(ji)(ji)械的(de)(de)(de)要求(qiu)。隨著(zhu)溫(wen)度(du)(du)的(de)(de)(de)降低，潤滑油(you)(you)粘度(du)(du)增(zeng)大，流動(dong)性變(bian)差，流到摩(mo)擦(ca)零件(jian)表面(mian)的(de)(de)(de)時(shi)(shi)間(jian)(jian)就會延長。潤滑油(you)(you)到達(da)摩(mo)擦(ca)表面(mian)所經歷的(de)(de)(de)時(shi)(shi)間(jian)(jian)越(yue)(yue)(yue)長，摩(mo)擦(ca)表面(mian)間(jian)(jian)金屬直(zhi)接(jie)接(jie)觸的(de)(de)(de)可能性越(yue)(yue)(yue)大，零件(jian)的(de)(de)(de)磨(mo)損(sun)(sun)也就加劇(ju)。發(fa)動(dong)機(ji)(ji)(ji)起(qi)動(dong)時(shi)(shi)，由于摩(mo)擦(ca)表面(mian)間(jian)(jian)缺油(you)(you)，這(zhe)時(shi)(shi)的(de)(de)(de)磨(mo)損(sun)(sun)量(liang)往往比正常運(yun)轉時(shi)(shi)增(zeng)大數倍。從總的(de)(de)(de)磨(mo)損(sun)(sun)量(liang)來看，起(qi)動(dong)時(shi)(shi)產(chan)生的(de)(de)(de)磨(mo)損(sun)(sun)約占(zhan)發(fa)動(dong)機(ji)(ji)(ji)磨(mo)損(sun)(sun)量(liang)的(de)(de)(de)2/3，而發(fa)動(dong)機(ji)(ji)(ji)工作期間(jian)(jian)所產(chan)生的(de)(de)(de)磨(mo)損(sun)(sun)僅占(zhan)1/3。起(qi)動(dong)時(shi)(shi)的(de)(de)(de)磨(mo)損(sun)(sun)還與發(fa)動(dong)機(ji)(ji)(ji)的(de)(de)(de)熱狀態有關，熄火后停(ting)(ting)(ting)車的(de)(de)(de)時(shi)(shi)間(jian)(jian)愈長，再(zai)次(ci)起(qi)動(dong)時(shi)(shi)的(de)(de)(de)磨(mo)損(sun)(sun)也越(yue)(yue)(yue)大。這(zhe)是(shi)因為停(ting)(ting)(ting)車的(de)(de)(de)時(shi)(shi)間(jian)(jian)越(yue)(yue)(yue)長，發(fa)動(dong)機(ji)(ji)(ji)溫(wen)度(du)(du)越(yue)(yue)(yue)低，潤滑油(you)(you)流動(dong)較困難(nan)。同(tong)時(shi)(shi)，停(ting)(ting)(ting)車時(shi)(shi)間(jian)(jian)長則從摩(mo)擦(ca)面(mian)流失的(de)(de)(de)油(you)(you)也較多，因而再(zai)次(ci)起(qi)動(dong)時(shi)(shi)則難(nan)以保證(zheng)流體潤滑。

    2.粘(zhan)度增大對低溫起動的影響

    潤滑(hua)油(you)的(de)(de)(de)低(di)(di)(di)溫(wen)(wen)枯度還影(ying)響(xiang)到(dao)機(ji)械設備(bei)的(de)(de)(de)起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)問題。一般認為(wei)活塞式發(fa)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)機(ji)起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)時的(de)(de)(de)zui大(da)粘度約為(wei)7600mm2/s，齒輪傳(chuan)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)裝置啟(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)時的(de)(de)(de)zui大(da)粘度約為(wei)162000mm2/s。上(shang)述起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)zui大(da)粘度只(zhi)是(shi)(shi)一概略的(de)(de)(de)經驗數據，對于(yu)其體設備(bei)來(lai)說(shuo)，可(ke)能會(hui)有(you)較大(da)的(de)(de)(de)出入，這是(shi)(shi)因(yin)為(wei)機(ji)械設備(bei)的(de)(de)(de)啟(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)問題牽涉的(de)(de)(de)因(yin)素(su)很多。例如(ru)起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)時所(suo)用(yong)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)力的(de)(de)(de)大(da)小(xiao)，機(ji)械的(de)(de)(de)技術狀況，以及(ji)燃料的(de)(de)(de)影(ying)響(xiang)等。但是(shi)(shi)從潤滑(hua)油(you)方面來(lai)講，粘度小(xiao)有(you)利于(yu)起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)，粘度大(da)則起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)困(kun)難(nan)。在氣溫(wen)(wen)很低(di)(di)(di)的(de)(de)(de)嚴寒(han)區行駛的(de)(de)(de)車輛，多用(yong)粘度較低(di)(di)(di)的(de)(de)(de)多級油(you)或輕質潤滑(hua)油(you)來(lai)潤滑(hua)發(fa)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)機(ji)，以保(bao)證低(di)(di)(di)溫(wen)(wen)下發(fa)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)機(ji)的(de)(de)(de)起(qi)動(dong)(dong)(dong)(dong)(dong)(dong)(dong)(dong)。

    此外，在(zai)寒冷(leng)的(de)季節使(shi)(shi)用(yong)粘度(du)較(jiao)大(da)的(de)潤滑油(you)還會使(shi)(shi)潤滑系統(tong)受(shou)到損壞。因(yin)為潤滑油(you)粘度(du)增(zeng)大(da)以后(hou)，潤滑系統(tong)內(nei)驅使(shi)(shi)油(you)液流動的(de)壓力也要增(zeng)大(da)，當壓力超(chao)過一定限度(du)后(hou)，則可能使(shi)(shi)油(you)管接頭(tou)等部件(jian)破(po)裂。