Hydraulic pump according to the working principle can be divided into four types, as follows.
1, gear pump
Small volume, simple structure, oil cleanliness requirements are not strict, cheaper price; But pump shaft by unbalanced force, wear serious, leakage. External gear pump when gear rotates in A cavity, due to the release of gear tooth to gradually increase volume, vacuum formed from the fuel tank of oil absorption, as the rotation of the gear oil full of inside the tooth was taken to B cavity, cavity in country B, because the tooth mesh, volume decreases, the hydraulic oil discharge using the tooth and the pump shell forming closed volume changes, complete the function of the pump.
2. Vane pump
It is divided into double-acting vane pump and single-acting vane pump. This pump flow uniformity, smooth operation, low noise, working pressure and volume efficiency than gear pump high, more complex than gear pump structure. Under the action of centrifugal force and pressure oil, the blade tip sticks to the inner surface of the stator as the rotor rotates. Such two blades and rotor and stator internal surface constituted by the working volume, first from small to large oil absorption and then from large to small oil discharge, when the blade rotation, two oil absorption and two oil discharge by inserting the rotor slot between the volume changes, to complete the role of the pump.
3. Plunger pump
High volume efficiency, small leakage, can work under high pressure, mostly used in high power hydraulic system; But the structure is complex, the material and the processing precision request is high, the price is expensive, the oil cleanliness request is high. Generally in gear pump and blade pump can not meet the requirements of the plunger pump. There are some other forms of hydraulic pump, such as screw pump, but the application is not as common as the above three. Plunger pump is composed of cylinder block and plunger, plunger reciprocating movement in the cylinder block, oil absorption when the working volume increases, working volume reduces oil discharge hour. The radial load of end face oil distribution is balanced by the large bearing around the cylinder block, so as to limit the inclination of the cylinder block to use the distribution plate distribution drive shaft only transfer torque, small diameter. Because of the inclining moment of the cylinder block, the manufacturing precision is required to be higher, otherwise it is easy to damage the distribution plate.
4, screw pump
One active screw meshes with two driven screws, and the meshing line of three screws divides the spiral groove into several sealing volumes. When the screw rotating, the sealing volume along the axial movement to achieve the absorption and drainage of oil using the screw groove content of the movement, the role of the pump can not be variable no flow pulsation radial load than the twin screw type small, large size, large mass.
