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。軸向柱塞泵除閥式配流外，其它形式原則上都可以作為液壓馬達用，即軸向柱塞泵和軸向柱塞馬達是可逆的。軸向柱塞馬達的工作原理為，配油盤和斜盤固定不動，馬達軸與缸體相連接一起旋轉。當壓力油經配油盤的窗口進入缸體的柱塞孔時，柱塞在壓力油作用下外伸，緊貼斜盤，斜盤對柱塞產生一個法向反力p，此力可分解為軸向分力及和垂直分力Q。Q與柱塞上液壓力相平衡，而Q則使柱塞對缸體中心產生一個轉矩，帶動馬達軸逆時針方向旋轉。軸向柱塞馬達產生的瞬時總轉矩是脈動的。若改變馬達壓力油輸入方向，則馬達軸按順時針方向旋轉。斜盤傾角a的改變、即排量的變化，不僅影響馬達的轉矩，而且影響它的轉速和轉向。斜盤傾角越大，產生轉矩越大，轉速越低。

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. Except for valve type flow distribution, other forms of axial piston pump can be used as hydraulic motor in principle, that is, axial piston pump and axial piston motor are reversible. The working principle of axial piston motor is that the oil distribution plate and swashplate are fixed, and the motor shaft is connected with the cylinder block and rotates together. When the pressure oil enters the plunger hole of the cylinder block through the window of the oil distribution plate, the plunger extends under the action of the pressure oil and clings to the swashplate. The swashplate generates a normal reaction force P to the plunger, which can be divided into axial component and vertical component Q. Q is balanced with the hydraulic pressure on the plunger, and Q causes the plunger to produce a torque to the center of the cylinder block, driving the motor shaft to rotate counterclockwise. The instantaneous total torque produced by the axial piston motor is pulsating. If the input direction of motor pressure oil is changed, the motor shaft rotates clockwise. The change of swashplate inclination a, that is, the change of displacement, affects not only the torque of the motor, but also its speed and steering. The greater the inclination angle of the swashplate, the greater the torque and the lower the speed.