Working principle of hydraulic motor

Working principle of hydraulic motor

1. Blade type hydraulic motor

Due to the action of pressure oil, the unbalanced force causes the rotor to generate torque. The output torque of a blade type 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 rate of the input hydraulic motor. Since hydraulic motors generally require the ability to rotate in both forward and reverse directions, the blades of blade type hydraulic motors need to be placed radially. In order to ensure that there is always pressure oil flowing through the root of the blade, a one-way valve should be installed on the path connecting the return and pressure oil chambers to the root of the blade. To ensure that the blade type hydraulic motor can start normally after the pressure oil flows through, the top of the blade and the inner surface of the stator must be in close contact to ensure good sealing. Therefore, a pre tension spring should be installed at the root of the blade. The blade type hydraulic motor has a small volume, low moment of inertia, and sensitive action, making it suitable for situations with high commutation frequency. However, it has a large leakage and is unstable when working at low speeds. Therefore, blade type hydraulic motors are generally used in situations where high speed, low torque, and sensitive action are required.

2. Radial piston hydraulic motor

The working principle of radial piston hydraulic motor is that 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 tightly presses against the inner wall of the stator, due to the eccentricity between the stator and the cylinder body. At the contact point between the plunger and the stator, the reaction force of the stator on the plunger is. Force can be decomposed into two component forces. When the oil pressure acting on the bottom of the plunger is p, the plunger diameter is d, and the angle between the force and X is X, the force generates a torque on the cylinder body, causing it to rotate. The cylinder body outputs torque and speed outward through a transmission shaft connected to the end face.

The situation where a plunger generates torque analyzed above, due to the presence of several plungers acting in the oil pressure zone, the torque generated on these plungers causes the cylinder body to rotate and output torque. Radial piston hydraulic motors are commonly used in low-speed and high torque situations.

3. Axial piston motor

Except for valve type distribution, axial piston pumps can generally be used as hydraulic motors in other forms, that is, axial piston pumps and axial piston motors are reversible. The working principle of an axial piston motor is that the oil distribution plate and the inclined plate are fixed, and the motor shaft is connected to the cylinder body and rotates together. When the pressure oil enters the plunger hole of the cylinder through the window of the oil distribution plate, the plunger extends outward under the action of the pressure oil, and closely adheres to the inclined plate, generating a normal reaction force p on the plunger. This force can be decomposed into axial component force and vertical component force Q. Q is balanced with the hydraulic pressure on the plunger, and Q causes the plunger to generate a torque on the center of the cylinder, driving the motor shaft to rotate counterclockwise. The instantaneous total torque generated by the axial piston motor is pulsating. If the direction of the motor pressure oil input is changed, the motor shaft will rotate clockwise. The change in the inclination angle a of the inclined plate, that is, the change in displacement, not only affects the torque of the motor, but also its speed and steering. The larger the inclination angle of the inclined plate, the greater the torque generated and the lower the speed.

4. Gear hydraulic motor

Gear motors, in order to meet the requirements of forward and reverse rotation, have equal inlet and outlet ports, symmetry, and a separate oil outlet to extract the leaked oil from the bearing part outside the housing; To reduce the starting friction torque, rolling bearings are used; In order to reduce torque pulsation, the gear hydraulic motor has more teeth than the pump.

Gear hydraulic motors have poor dry sealing and low capacity efficiency, and the input oil pressure cannot be too high to generate large torque. And the instantaneous speed and torque vary with the position of the meshing point, so gear hydraulic motors are only suitable for high-speed and low torque situations. Generally used on dry engineering machinery, agricultural machinery, and mechanical equipment with low requirements for torque uniformity.