傳(chuan)動比是(shi)機構(gou)(gou)中兩(liang)轉(zhuan)動構(gou)(gou)件角速(su)度(du)的(de)比值，也稱(cheng)速(su)比。構(gou)(gou)件a和(he)構(gou)(gou)件b的(de)傳(chuan)動比為(wei)i=ωa/ ωb=na/nb，式(shi)中ωa和(he) ωb分別為(wei)構(gou)(gou)件a和(he)b的(de)角速(su)度(du)（弧度(du)/秒）；na和(he)nb分別為(wei)構(gou)(gou)件a和(he)b的(de)轉(zhuan)速(su)（轉(zhuan)/分）。

當(dang)(dang)式中的角速度為瞬(shun)時(shi)(shi)值時(shi)(shi)，則求(qiu)得的傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比為瞬(shun)時(shi)(shi)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比。當(dang)(dang)式中的角速度為平均值時(shi)(shi)，則求(qiu)得的傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比為平均傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比。理論上對(dui)(dui)于大多數漸開線齒(chi)廓正(zheng)確的齒(chi)輪(lun)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)，瞬(shun)時(shi)(shi)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比是不變(bian)(bian)的；對(dui)(dui)于鏈(lian)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)和(he)(he)(he)摩擦(ca)輪(lun)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)，瞬(shun)時(shi)(shi)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比是變(bian)(bian)化的。對(dui)(dui)于嚙合(he)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)，傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比可用a和(he)(he)(he)b輪(lun)的齒(chi)數Za和(he)(he)(he)Zb表(biao)示(shi)，i=Zb/Za；對(dui)(dui)于摩擦(ca)傳(chuan)(chuan)動(dong)(dong)(dong)(dong)，傳(chuan)(chuan)動(dong)(dong)(dong)(dong)比可用a和(he)(he)(he)b輪(lun)的直徑Da和(he)(he)(he)Db表(biao)示(shi)，i=Db/Da。

計算方法：

傳動比=使(shi)用(yong)扭(niu)矩÷9550÷電機功率×電機功率輸入轉數÷使(shi)用(yong)系數

傳動比=主動輪(lun)轉(zhuan)速除(chu)以從動輪(lun)轉(zhuan)速的值(zhi)=它們分(fen)度圓直徑比值(zhi)的倒數(shu)。即：i=n1/n2=D2/D1

i=n1/n2=z2/z1（齒輪(lun)的）

對(dui)于(yu)多級(ji)齒輪(lun)傳(chuan)動(dong)(dong)：1.每兩(liang)軸之間的(de)傳(chuan)動(dong)(dong)比(bi)按照上面(mian)的(de)公式(shi)計算(suan)。 2.從第一軸到第n軸的(de)總(zong)傳(chuan)動(dong)(dong)比(bi)等于(yu)各級(ji)傳(chuan)動(dong)(dong)比(bi)之積(ji)