由于壓力油作用，受力不平衡使轉子產生轉矩。葉片式液壓馬達的輸出轉矩與液壓馬達的排量和液壓馬達進出油口之間的壓力差有關，其轉速由輸入液壓馬達的流量大小來決定。由于液壓馬達一般都要求能正反轉，所以葉片式液壓馬達的葉片要徑向放置。為了使葉片根部始終通有壓力油，在回、壓油腔通入葉片根部的通路上應設置單向閥，為了確保葉片式液壓馬達在壓力油通入后能正常啟動，必須使葉片頂部和定子內表面緊密接觸，以保證良好的密封，因此在葉片根部應設置預緊彈簧。葉片式液壓馬達體積小、轉動慣量小、動作靈敏、可適用于換向頻率較高的場合；但泄漏量較大、低速工作時不穩(wěn)定。因此葉片式液壓馬達一般用于轉速高、轉矩小和動作要求靈敏的場合。徑向柱塞式液壓馬達工作原理，當壓力油經固定的配油軸4的窗口進入缸體內柱塞的底部時，柱塞向外伸出，緊緊頂住定子的內壁，由于定子與缸體存在一偏心距。在柱塞與定子接觸處，定子對柱塞的反作用力為 。力可分解為和 兩個分力。當作用在柱塞底部的油液壓力為p，柱塞直徑為d，力和之間的夾角為X時，力對缸體產生一轉矩，使缸體旋轉。缸體再通過端面連接的傳動軸向外輸出轉矩和轉速。以上分析的一個柱塞產生轉矩的情況，由于在壓油區(qū)作用有好幾個柱塞，在這些柱塞上所產生的轉矩都使缸體旋轉，并輸出轉矩。徑向柱塞液壓馬達多用于低速大轉矩的情況下。

Due to the action of pressure oil, the unbalanced force makes the rotor produce torque. The output torque of the vane hydraulic motor is related to the displacement of the hydraulic motor and the pressure difference between the inlet and outlet of the hydraulic motor, and its speed is determined by the flow of the input hydraulic motor. Since hydraulic motors generally require positive and negative rotation, the blades of vane hydraulic motors should be placed radially. In order to ensure that the blade root is always filled with pressure oil, a check valve should be set on the path from the return and pressure oil chamber to the blade root. In order to ensure that the blade type hydraulic motor can start normally after the pressure oil is connected, the top of the blade must be in close contact with the inner surface of the stator to ensure a good seal. Therefore, a pre tightening spring should be set at the blade root. The vane hydraulic motor has small volume, small moment of inertia, sensitive action, and can be used in occasions with high commutation frequency; However, the leakage is large and unstable at low speed. Therefore, vane hydraulic motors are generally used in occasions with high speed, small torque and sensitive action requirements. Working principle of radial plunger hydraulic motor: when the pressure oil enters the bottom of the plunger in the cylinder through the window of the fixed oil distribution shaft 4, the plunger extends outward and firmly presses against the inner wall of the stator, because there is an eccentric distance between the stator and the cylinder block. At the contact between the plunger and the stator, the reaction force of the stator on the plunger is. The force can be decomposed into two components, and. When the oil pressure acting on the bottom of the plunger is p, the diameter of the plunger is D, and the included angle between the force and is x, the force generates a torque on the cylinder block to make the cylinder block rotate. The cylinder block then outputs torque and speed through the transmission shaft connected to the end face. In the case of a plunger generating torque analyzed above, because there are several plungers acting in the oil pressure area, the torque generated on these plungers rotates the cylinder block and outputs torque. Radial piston hydraulic motors are mostly used in the case of low speed and high torque.