According to the working principle, hydraulic pumps can be divided into the following four types.
1, gear pump
Small size, simple structure, low requirement for oil cleanliness and low price; However, the pump shaft is subjected to unbalanced force, which causes serious wear and leakage. ? External gear pump? When the gear rotates, in the cavity A, due to the disengagement of the gear teeth, the volume gradually increases, forming a vacuum and sucking oil from the oil tank. With the rotation of the gear, the oil filled in the tooth slot is brought to the B cavity. In the B cavity, the volume is gradually reduced due to the meshing of the gear teeth, and the hydraulic oil is discharged? The function of the pump is completed by the change of the closed volume formed by the teeth and the pump shell.
2. vane pump?
Divided into double-acting vane pump and single-acting vane pump. Compared with gear pump, this pump has the advantages of uniform flow, stable operation, low noise, high working pressure and volumetric efficiency, and its structure is also more complicated than gear pump. ? When the rotor rotates, under the action of centrifugal force and pressure oil, the blade tip clings to the inner surface of the stator. In this way, the working volume formed by the two blades and the inner surfaces of the rotor and stator first absorbs oil from small to large, and then discharges oil from large to small. When the blade rotates once, it can absorb oil twice and discharge oil twice. The function of the pump is accomplished by using the volume change between blades inserted into the rotor slot.
3. Piston pump
High volumetric efficiency, small leakage, can work under high pressure, and is mostly used in high-power hydraulic systems; However, the structure is complex, the requirements for materials and processing accuracy are high, the price is expensive and the cleanliness of oil is high. Generally, piston pumps are only used when gear pumps and vane pumps cannot meet the requirements. There are other forms of hydraulic pumps, such as screw pumps, but their applications are not as common as the above three. ? Piston pump consists of cylinder and plunger. The plunger reciprocates in the cylinder, absorbing oil when the working volume increases and discharging oil when the working volume decreases. Use end face oil distribution? The radial load is balanced by the big bearing on the periphery of the cylinder block to limit the inclination of the cylinder block. The port plate is only used to transmit torque, and the shaft diameter is small. Because of the tilting moment of the cylinder block, it is required to have high manufacturing accuracy, otherwise it is easy to damage the port plate. ?
4. Screw pump
A driving screw and two driven screws mesh with each other, and the meshing lines of the three screws divide the spiral groove into several closed volumes. When the screw rotates, the sealed volume moves along the axial direction to realize oil absorption and oil discharge. Using the movement of the internal volume of the spiral groove, the function of the pump is unchanged, and the radial load without flow pulsation is smaller, larger and heavier than that of the twin-screw type.