中文摘要：

以某款8档自动变速器（8AT）为研究对象,该变速器行星齿轮机构由4个单行星齿轮行星排和5个换挡执行元件构成.首先列写出行星齿轮机构的运动规律方程式.因为4个行星排都是单行星齿轮机构,所以各行星排的运动规律方程式是相同的.根据各档中离合器和制动器的动作顺序,并结合机构联接关系,列写运动规律方程组,求出每一档位的传动比.根据各档传动比公式和实际传动比数值可以计算出各行星排齿圈齿数和太阳轮齿数之比,验证了公式的准确性.为自动变速器动力路线分析、设计及控制奠定了理论基础.

英文摘要：

Researches on a 8 speed automatic transmission （8AT）,which is composed of 4 planetary gearsets and 5 shift elements.First the motion equation of the planetary gear mechanism is induced.Because all the gearsets are single planetary gear,and motion equation is the same.According to the action sequence of the clutch and brake,combined with the relationship between the planetary gears,the motion equations are written out and every gear ratio formula is found out.Based on the gear ratio formula and the ratio value,the gear ratio of ring to sun is calculated,the formula is verified correctly.The theoretical foundation for analysis,design and control of automatic transmission is established.