Working principle of variable displacement motor

Variable displacement motor is a hydraulic motor with variable displacement and theoretical input. It is often used in cranes and other heavy load, high-precision machinery, and rely on regulators to control the size of the displacement to achieve the desired demand. The initial displacement of the motor is large. When the working pressure is lower than the set pressure of the valve 7, the valve 7 does not play a control role. The displacement of the motor changes steplessly between large and small with the change of the X port pilot control pressure, so as to realize the pilot pressure control. When the pressure oil is supplied by any working oil port of motor A and B, the pressure oil can enter the small chamber of variable cylinder 5 through one-way valve. When the pilot control pressure of port x increases, the force of pilot control pressure oil acting on valve 1 will overcome the combined force of pressure regulating spring 2 and spring 3, and push valve 1 to move to the right. When the pilot control pressure increases to the starting pressure of motor variable, valve 1 will be in the middle position.

If the pilot control pressure continues to rise, the servo valve core will further move to the right, the servo valve 1 is in the left position function, and the motor working pressure oil enters the variable cylinder 5 chamber through valves 1 and 7. Because the area of both ends of variable piston 6 is not equal, when both ends are affected by pressure oil, the variable piston will move to the left, and the shift rod fixed on the variable piston will drive the oil distribution plate and cylinder block to swing, thus reducing the angle between the cylinder block and the main shaft, thus reducing the motor displacement. When the control pressure of the X port decreases, the control process of the motor is opposite to the above process, which will not be repeated here. To sum up, when the pilot control pressure changes between the variable starting pressure and the variable ending pressure, the motor displacement will change between large and small.