ZLY是硬齒(chi)面(mian)圓柱齒(chi)輪減(jian)速機，N是帶(dai)逆止器(qi)，125是中心(xin)距(ju)，20是速比，1是裝配(pei)形(xing)式。

減(jian)速機(ji)在原動機(ji)和(he)(he)工(gong)作機(ji)或(huo)執(zhi)行機(ji)構(gou)之(zhi)間起(qi)匹配轉(zhuan)速和(he)(he)傳(chuan)遞轉(zhuan)矩的作用，是一種相對精密的機(ji)械。

使(shi)用(yong)(yong)它的目(mu)的是降低轉速，增(zeng)加轉矩。它的種類繁多，型號各異，不同種類有不同的用(yong)(yong)途。

減(jian)(jian)(jian)速(su)器(qi)的種類繁(fan)多(duo)(duo)，按(an)照(zhao)傳動(dong)類型可(ke)分(fen)(fen)為(wei)齒(chi)(chi)輪(lun)(lun)減(jian)(jian)(jian)速(su)器(qi)、蝸桿減(jian)(jian)(jian)速(su)器(qi)和(he)行星齒(chi)(chi)輪(lun)(lun)減(jian)(jian)(jian)速(su)器(qi)；按(an)照(zhao)傳動(dong)級數不(bu)同可(ke)分(fen)(fen)為(wei)單級和(he)多(duo)(duo)級減(jian)(jian)(jian)速(su)器(qi)；按(an)照(zhao)齒(chi)(chi)輪(lun)(lun)形狀可(ke)分(fen)(fen)為(wei)圓(yuan)柱(zhu)齒(chi)(chi)輪(lun)(lun)減(jian)(jian)(jian)速(su)器(qi)、圓(yuan)錐(zhui)齒(chi)(chi)輪(lun)(lun)減(jian)(jian)(jian)速(su)器(qi)和(he)圓(yuan)錐(zhui)－圓(yuan)柱(zhu)齒(chi)(chi)輪(lun)(lun)減(jian)(jian)(jian)速(su)器(qi)；按(an)照(zhao)傳動(dong)的布置形式(shi)(shi)(shi)又可(ke)分(fen)(fen)為(wei)展(zhan)開式(shi)(shi)(shi)、分(fen)(fen)流式(shi)(shi)(shi)和(he)同軸式(shi)(shi)(shi)減(jian)(jian)(jian)速(su)器(qi)。