目前低速大扭矩液压马达多采用柱塞元件、齿轮偏摆和齿轮摆线式等。因其结构复杂、零件多、精度要求很高和相对体积较大,不少产品仍处在研制阶段,尚不能满足生产发展的要求。至于低速大扭矩叶片式油马达按现有产品的YM型结构就很难实现。由于生产发展需要,设计YMD型低速大扭矩叶片式油马达的工作于1978年上半年完成,并于同年10月至1979年2月初研制成功 At present, low-speed large torque hydraulic motors use more plunger components, gear deflection and gear cycloidal and so on. Because of its complex structure, many parts, high precision and relatively large size, many products are still in the development stage, still can not meet the requirements of the development of production. As for the low-speed high-torque vane oil motor YM-type structure of existing products is very difficult to achieve. Due to the needs of production and development, the work of designing YMD low-speed and large-torque vane oil motor was completed in the first half of 1978 and was successfully developed from October to early February 1979