Views: 5 Author: Site Editor Publish Time: 2020-10-19 Origin: Site
A hydraulic pump is a hydraulic component that provides pressurized liquid for hydraulic transmission, and is a kind of pump. Although the structure of different types of hydraulic pumps is quite different, there are many common points in installation, use and maintenance. If the operation is not standardized, it may cause failures.
The function of the hydraulic pump is to convert the mechanical energy of power machines (such as electric motors and internal combustion engines) into pressure energy of liquids. The output flow can be adjusted according to needs is called a variable pump, and the flow cannot be adjusted is called a quantitative pump.
Although the structure of hydraulic pumps is quite different, there are many common points in installation and use.
一. Types of commonly used hydraulic pumps
1. According to whether the flow can be adjusted, it can be divided into: variable pump and fixed pump. The output flow can be adjusted according to needs is called a variable pump, and the flow cannot be adjusted is called a quantitative pump.
2. According to the commonly used pump structure in hydraulic system, it is divided into three types: gear pump, vane pump and plunger pump.
Gear pump: small in size, simple in structure, less demanding on oil cleanliness, and cheaper in price; but the pump shaft is subject to unbalanced force, severe wear and large leakage.
Vane pump: divided into double-acting vane pump and single-acting vane pump. This kind of pump has uniform flow, stable operation, low noise, higher working pressure and volumetric efficiency than gear pumps, and more complicated structure than gear pumps.
Plunger pump: high volumetric efficiency, small leakage, can work under high pressure, mostly used in high-power hydraulic systems; but the structure is complex, the material and processing accuracy requirements are high, the price is expensive, and the oil cleanliness requirements are high.
Generally, plunger pumps are used when gear pumps and vane pumps cannot meet the requirements. There are other types of hydraulic pumps, such as screw pumps, but their applications are not as common as the above three types.
二.The working principle of hydraulic pump
1. Plunger pump
Piston pumps are divided into two representative structural forms: axial piston pumps and radial piston pumps; since radial piston pumps are a new type of high-efficiency pump with relatively high technical content, with the continuous acceleration of localization , The radial piston pump will inevitably become an important part of the application field of the piston pump.
Plunger pump is a kind of reciprocating pump, which belongs to volumetric pump. Its plunger is driven by the eccentric rotation of the pump shaft and moves back and forth. Its suction and discharge valves are both check valves. When the plunger is pulled out, the pressure in the working chamber decreases and the outlet valve closes. When the pressure is lower than the inlet pressure, the inlet valve opens and liquid enters; when the plunger is pushed in, the working chamber pressure rises and the inlet valve closes. When the pressure is higher than the outlet pressure, The outlet valve opens and the liquid is discharged.
The axial piston pump with sliding shoe structure is currently the most widely used axial piston pump. The plunger placed in the cylinder is in contact with the swash plate through the sliding shoe. When the drive shaft drives the cylinder to rotate, the swash plate Pull or push the plunger out of the cylinder to complete the oil suction and discharge process. The oil in the working cavity formed by the plunger and the cylinder bore is respectively communicated with the suction and discharge cavities of the pump through an oil distribution plate. The variable mechanism is used to change the inclination angle of the swash plate, and the pump displacement can be changed by adjusting the inclination angle of the swash plate.
2. Vane pump
Working principle of double-acting pump:
It consists of stator, rotor, blades and oil distribution plate. The inner wall of the stator is approximately elliptical. The blades are installed in the radial slots of the rotor and can slide along the slots, and the rotor and the stator are installed concentrically. When the rotor rotates, the blades are pressed against the inner surface of the stator under the action of centrifugal force, and are forced to slide back and forth in the rotor slot as the curve of the inner surface of the stator changes. The sealed working cavity between two adjacent blades increases and shrinks. Variety. When the blade slides from a small radius arc to a large radius arc, the sealed working chamber gradually increases to form a partial vacuum, so the oil in the oil tank is sucked in through the oil suction chamber on the oil distribution plate; otherwise, the oil is forced out. For each revolution of the rotor, the blade slides back and forth twice in the groove, completing 2 times of oil absorption and 2 times of oil pressure, and the radial force generated by the oil pressure is balanced, so it is called double-acting type, also called balanced type.
Working principle of single-acting vane pump:
It is mainly composed of stator, rotor, blade and oil distribution plate. The inner surface of the stator is a cylindrical shape, the rotor is eccentrically installed in the stator, that is, there is an eccentricity e. The blades are installed in the radial sliding groove of the rotor and can slide radially in the groove. When the rotor rotates, under the action of centrifugal force and the pressure oil at the root of the blade, the blade is closely attached to the inner surface of the stator, so that a sealed working cavity is formed between two adjacent blades. On one side, the blades gradually extend, and the sealed working chamber gradually increases, forming a partial vacuum, forming oil absorption; on the other hand, forming oil pressure. For every revolution of the rotor, the blade slides back and forth in the chute once to complete one oil suction and one oil pressure. The radial force generated by the oil pressure is unbalanced, so it is called single-acting or unbalanced vane pump.
3. Gas booster pump
Working principle of gas booster pump
The pneumatic booster pump is mainly driven by the low pressure gas at the piston end of the large area to generate high pressure fluid at the piston end of the small area. It can be used for compressed air and other gases, and the output air pressure can be steplessly adjusted by driving air pressure.
Pneumatic booster pumps are driven by low-pressure gas at the piston end with a large area to generate high-pressure fluid at the piston end with a small area. It can be used for compressed air and other gases, and the output air pressure can be steplessly adjusted by driving air pressure.
Multiple gas drives: compressed air, liquefied nitrogen, pipeline nitrogen, water vapor.