TQY - 4型拖牵机与旧拖牵机的最大区别在于改机械传动为液压传动。液压传动系统能在较大范围内实现有载无级变速、有载停机、启动和反向转动 ,实现对牵引工况的有效监控和过载保护 ,操作简单 ,寿命长。设计的重点是液压系统参数的确定 ,主要设备和辅助元件的选择及其有关计算。 The biggest difference between the TQY-4 towing machine and the towing machine is the change of mechanical transmission to hydraulic transmission. Hydraulic transmission system can achieve a wide range of load continuously variable transmission, load shutdown, start and reverse rotation, to achieve effective monitoring of the traction conditions and overload protection, simple operation, long life. The focus of the design is the determination of hydraulic system parameters, the selection of the main equipment and auxiliary components and their related calculations.