Working principle of hydraulic motor
1. Vane type hydraulic motor
Due to the pressure oil, the force imbalance makes the rotor produce torque. The output torque of the vane 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. As the hydraulic motor is generally required to be able to reverse, so the blade of vane type hydraulic motor should be placed radially. In order to make the blade root always filled with pressure oil, a one-way valve should be set on the passage from the oil return and pressure chamber to the blade root. In order to ensure that the blade type hydraulic motor can start normally after the pressure oil is filled, the top of the blade must be in close contact with the inner surface of the stator to ensure good sealing. Therefore, a pre tightening spring should be set at the blade root. The vane type hydraulic motor has small volume, small moment of inertia and sensitive action. It can be applied to the occasions with high commutation frequency, but it has large leakage and is unstable at low speed. Therefore, the vane type hydraulic motor is generally used in the occasions with high speed, small torque and sensitive action requirements.
2. Radial piston hydraulic motor
The working principle of the radial piston type hydraulic motor is that when the pressure oil enters the bottom of the piston in the cylinder body through the window of the fixed oil distribution shaft 4, the piston extends outwards 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 point between the plunger and the stator, the reaction force between the stator and the plunger is. The force can be divided into two parts. When the oil pressure acting on the bottom of the plunger is p, the diameter of the plunger is D, and the angle between the force and is x, the force produces a torque on the cylinder block and makes the cylinder block rotate. The cylinder block then outputs the torque and speed through the transmission shaft connected with the end face.
The above analysis of a plunger torque, because there are several plunger in the oil pressure zone, the torque generated on these plunger makes the cylinder block rotate, and output torque. Radial piston hydraulic motor is mostly used in the case of low speed and high torque.
3. Axial piston motor
In principle, axial piston pump can be used as hydraulic motor except valve type flow distribution, that is, axial piston pump and axial piston motor are reversible. The working principle of the axial piston motor is that the oil distribution plate and swash plate 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 out under the action of the pressure oil and clings to the swashplate. The swashplate produces a normal reaction force P on the plunger, which can be divided 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 produce a torque to the center of the cylinder block, driving the motor shaft to rotate counterclockwise. The instantaneous total torque produced by axial piston motor is pulsating. If the input direction of motor pressure oil is changed, the motor shaft rotates clockwise. The change of swash plate angle a, that is, the change of displacement, not only affects the torque of the motor, but also affects its speed and steering. The greater the inclined angle of swash plate, the greater the torque and the lower the speed.
4. Gear hydraulic motor
In order to meet the requirements of forward and reverse rotation in the structure of gear motor, the oil inlet and outlet are equal and symmetrical, and there is a separate oil outlet to lead the leakage oil of bearing out of the shell; In order to reduce the starting friction torque, rolling bearing is used; In order to reduce torque ripple, the number of teeth of gear hydraulic motor is more than that of pump.
The gear hydraulic motor is characterized by poor dry sealing, low capacity efficiency, high input oil pressure and large torque. And the instantaneous speed and torque change with the position of the meshing point, so the gear hydraulic motor is only suitable for the situation of high speed and small torque. Generally used in dry construction machinery, agricultural machinery and machinery and equipment with low torque uniformity requirements.