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1、Lesson4DieselEngineConstruction(2)第4課柴油機(jī)結(jié)構(gòu)(2)Pistonsandpistonrods活塞及活塞桿Apistonconsistsofalowerpart-pistonskirtofcastiron-andaupperpartorcrownmadeofaspecialheat-resistantsteel.活塞由其下部——鑄鐵制成的活塞裙,以及上部——耐熱鋼制成的活塞頭組成。Theyareboltedtogetherandfixedtothepistonrod.它們用螺栓連在一起并固定在活塞桿上。
2、Thepositionofthepistonpartsinrelationtoeachotherissecuredbymeansofmachine-turnedrecessesandadowelpininthecrown.活塞部件相互間的位置由活塞頭上車削的凹槽和定位銷來固定。Eachpistonisprovidedwithfiveorsixpistonringsfittedinchromiumplatedgroovesinthecrown.每個活塞裝有五至六道活塞環(huán),活塞環(huán)裝在頭部鍍鉻的環(huán)槽中。Thetwoorthreetopmostr
3、ingsarenarrowringshavingdiagonalcuts,whilethenexttwoarebroadandareprovidedwithoverlappingendjoints.最上面的兩三道活塞環(huán)是帶斜切口的窄環(huán),緊接下去的兩道活塞環(huán)是帶有重疊搭口的寬環(huán)。Thelowestringisanoildistributorring.最下面的那道環(huán)是刮油環(huán)。Alltheringsareslightlyroundedontheexternaltopandbottomedgestokeeptheoilfilmonthecylin
4、derlinerduringtherunning-inperiodfornewpistonrings.所有活塞環(huán)頂部和底部的外緣都稍有倒角,以便在新活塞環(huán)磨合期間缸套上留有油膜。Inordertocontrolthermalstresses,thinwallintensivelycooledpistonsareusedforsometypesofmodernengines.為了控制熱應(yīng)力,某些現(xiàn)代柴油機(jī)采用薄壁集中冷卻活塞。Inthiscase,thepistonhasaninternalinsertinthepistoncrown,wh
5、ichservesonlytodirectthecoolingliquidflowand在這種情況下,活塞頭內(nèi)部有一插件,它用來對冷卻液流導(dǎo)向thereby,tointensifytheconventionalcocktailshaker'effect.由此可增強(qiáng)傳統(tǒng)的“雞尾震蕩”效應(yīng)。Thepistonrodsareboredfromthetopflangetoapointoppositethecenterofthecrosshead.活塞桿從頂部法蘭到與十字頭中心相對位置處銼孔。Throughthisbore,alongpipeisi
6、nsertedwhichgoesnearlytothebottomofthebore.一根長管從此插入接近孔底。Theoutsidediameterofthepipeislessthanthediameterofthebore,theresultbeingthatanannularspaceisformedbetweenthepistonrodandthepipe.管的外徑小于孔的直徑,因此在活塞桿和管子之間形成一個環(huán)形空間。Thelowerendofthepistonrodisreducedindiametertofitaboreint
7、hecrosshead,thisbeingsecuredtothepistonrodbyanut.活塞桿的下端直徑減小,插入十字頭內(nèi)孔中,并用螺帽將十字頭與活塞桿緊固。Thepistonrodsareprovidedwithdowelpinstoensurethecorrectassemblyofthecomponents.活塞桿上裝有定位銷,以確保各部件的正確裝配。Oneachofthetwojournalsofthecrosshead,crossheadshoesaremountedwhichareguidedinthebuilt-i
8、ncrossheadguidesoftheengineframe.在十字頭兩端軸頸處,各裝有十字頭滑塊。十字頭滑塊由發(fā)動機(jī)機(jī)架內(nèi)的一十字頭導(dǎo)板導(dǎo)向。Thepositionofthecrossh
