限矩(ju)型液(ye)(ye)力(li)偶合(he)(he)器(qi)(qi)(qi)充液(ye)(ye)過(guo)(guo)(guo)多，會(hui)使輸出力(li)矩(ju)提高，當偶合(he)(he)器(qi)(qi)(qi)輸出力(li)矩(ju)超(chao)過(guo)(guo)(guo)電(dian)(dian)動(dong)機和(he)工(gong)作機的額定力(li)矩(ju)之后(hou)(hou)，就會(hui)失去過(guo)(guo)(guo)載(zai)(zai)(zai)保護功能(neng)(neng)。這(zhe)是(shi)因為(wei)液(ye)(ye)力(li)偶合(he)(he)器(qi)(qi)(qi)是(shi)依(yi)靠(kao)加大滑(hua)差使偶合(he)(he)器(qi)(qi)(qi)發熱(re)，易熔塞噴(pen)液(ye)(ye)來實施過(guo)(guo)(guo)載(zai)(zai)(zai)保護的。若偶合(he)(he)器(qi)(qi)(qi)充液(ye)(ye)過(guo)(guo)(guo)多，就會(hui)使其傳(chuan)遞力(li)矩(ju)能(neng)(neng)力(li)過(guo)(guo)(guo)強，工(gong)作機超(chao)載(zai)(zai)(zai)之后(hou)(hou)，偶合(he)(he)器(qi)(qi)(qi)不超(chao)載(zai)(zai)(zai)，由于(yu)偶合(he)(he)器(qi)(qi)(qi)輸出力(li)矩(ju)等于(yu)輸入力(li)矩(ju)，所以將(jiang)超(chao)載(zai)(zai)(zai)力(li)矩(ju)傳(chuan)到(dao)電(dian)(dian)動(dong)機，使電(dian)(dian)動(dong)機超(chao)載(zai)(zai)(zai)，偶合(he)(he)器(qi)(qi)(qi)失去過(guo)(guo)(guo)載(zai)(zai)(zai)保護功能(neng)(neng)。

此外，如(ru)果偶合(he)器(qi)全充(chong)滿(man)油(you)(you)，則過載(zai)時工(gong)作腔(qiang)內(nei)的(de)油(you)(you)因輔(fu)助腔(qiang)已(yi)充(chong)滿(man)油(you)(you)而無(wu)法向輔(fu)助腔(qiang)分流，于是偶合(he)器(qi)的(de)力矩無(wu)法降低，失(shi)去過載(zai)保護功能。

液(ye)力(li)(li)(li)(li)偶合器(qi)的(de)基(ji)本構件是具有若干(gan)徑向葉片的(de)、構成(cheng)工(gong)(gong)作(zuo)腔的(de)泵(beng)輪(lun)(lun)和(he)渦輪(lun)(lun)。液(ye)力(li)(li)(li)(li)傳(chuan)動(dong)(dong)(dong)液(ye)在(zai)工(gong)(gong)作(zuo)腔里高速循(xun)環流(liu)動(dong)(dong)(dong)傳(chuan)遞動(dong)(dong)(dong)力(li)(li)(li)(li),傳(chuan)動(dong)(dong)(dong)液(ye)隨從泵(beng)輪(lun)(lun)做牽連運(yun)動(dong)(dong)(dong)的(de)同時因(yin)離(li)心力(li)(li)(li)(li)作(zuo)用而做離(li)心運(yun)動(dong)(dong)(dong),從泵(beng)輪(lun)(lun)吸收機械能并轉化為動(dong)(dong)(dong)量(liang)(liang)矩增(zeng)量(liang)(liang),并沖入渦輪(lun)(lun)做向心流(liu)動(dong)(dong)(dong)釋(shi)放動(dong)(dong)(dong)量(liang)(liang)矩,推(tui)動(dong)(dong)(dong)渦輪(lun)(lun)旋(xuan)轉,帶動(dong)(dong)(dong)工(gong)(gong)作(zuo)機做功。

限矩(ju)型液(ye)力偶合器(qi)充(chong)液(ye)過少，傳遞(di)功率不足，不能使工(gong)作(zuo)機(ji)(ji)在額(e)定(ding)工(gong)況下工(gong)作(zuo)。為(wei)了加大扭矩(ju)適應工(gong)作(zuo)機(ji)(ji)的需要，只好(hao)加大滑差、降低(di)轉速，在偏離額(e)定(ding)工(gong)況點下工(gong)作(zuo)。由于限矩(ju)型液(ye)力偶合器(qi)，即效率等于轉速比，所(suo)以滑差加大、轉速比降低(di)之后(hou)(hou)，效率降低(di)。效率降低(di)之后(hou)(hou)，偶合器(qi)損失的功率轉化成(cheng)的熱量增多(duo)，促使偶合器(qi)升溫，當(dang)達(da)到易熔(rong)塞(sai)的保(bao)護溫度之后(hou)(hou)，易熔(rong)塞(sai)便(bian)噴(pen)液(ye)保(bao)護，造成(cheng)偶合器(qi)頻繁噴(pen)液(ye)。