The hydraulic pump of a hydraulic lift is a hydraulic component that provides pressurized liquid for hydraulic transmission, and is a kind of pump. Its function is to convert the mechanical energy of the power machine (such as electric motors and internal combustion engines, etc.) into the pressure energy of the liquid. Output flow can be adjusted according to needs, called variable pump; Flow cannot be adjusted, called quantitative pump.
There are three kinds of pumps commonly used in the hydraulic system of hydraulic lift: gear pump, vane pump and plunger pump.
Gear pump: small volume, simple structure, the cleanliness of the oil is not strict, the price is cheaper, but the pump shaft is subject to unbalanced force, serious wear and leakage.
Vane pump: divided into double acting vane pump and single acting vane pump. The pump has uniform flow, smooth operation, low noise, higher working pressure and volumetric efficiency than gear pump, and more complex structure than gear pump.
Plunger pump: high volume 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 cleanliness of the oil is high. Generally, the plunger pump is used when the gear pump and blade pump cannot meet the requirements.
There are some other forms of hydraulic pumps, such as screw pumps, but the application is not as common as the above three.
Hydraulic pumps rely on the principle of sealing volume change to work, so it is generally called positive displacement hydraulic pump. The hydraulic pump of the hydraulic lift converts the mechanical energy input by the prime mover into the pressure energy of the liquid, the prime mover drives the eccentric to rotate continuously, and the hydraulic pump continuously absorbs oil and pressure oil.
Single plunger hydraulic pump has all the basic characteristics of positive displacement hydraulic pump:
(1) Has a number of sealed and can be periodically changed space. The output flow of the hydraulic pump is proportional to the volume change of this space and the number of changes per unit time, and has nothing to do with other factors. This is an important characteristic of positive displacement hydraulic pump.
(2) The absolute pressure of the liquid in the tank must be equal to or greater than the atmospheric pressure. This is the external condition that the positive displacement hydraulic pump can inhale the oil. Therefore, in order to ensure the normal oil absorption of the hydraulic pump, the tank must be connected with the atmosphere, or a closed pressurized tank must be used.
(3) With the corresponding distribution mechanism. The oil suction chamber and the liquid discharge chamber are separated to ensure that the hydraulic pump regularly and continuously sucks and drains liquid. The structure principle of hydraulic pump is different, and its oil distribution mechanism is also different.
The oil chamber in the positive displacement hydraulic pump is called the oil suction chamber when it is in the suction. The pressure of the oil suction chamber of the hydraulic lift depends on the oil suction height and the resistance of the oil suction line. If the oil suction height is too high or the resistance of the oil suction line is too large, the vacuum degree of the oil suction chamber is too high and the self-priming capacity of the hydraulic pump is affected. The oil chamber is called the oil chamber when the oil is pressed, and the pressure of the oil chamber depends on the external load and the pressure loss of the oil discharge line. Theoretically speaking, the oil discharge pressure has nothing to do with the flow of the hydraulic pump.
The theoretical flow rate of displacement hydraulic pump depends on the relevant geometric size and speed of hydraulic pump, and has nothing to do with the oil discharge pressure. The oil discharge pressure of the hydraulic lift will affect the internal leakage of the pump and the compression of the oil, thus affecting the actual output flow of the pump, so the actual output flow of the hydraulic pump decreases with the increase of the oil discharge pressure.
The hydraulic pump of the hydraulic lift is divided into two categories of quantitative pump and variable pump according to whether the volume of the oil that can be output per unit time can be adjusted, and can be divided into three categories of gear type, blade type and plunger type according to the structural form.
