A Discussion Based on Hydraulic Pump Power Components

The hydraulic pumps are the power hydraulic components of the hydraulic system, it is the device that converts the mechanical energy output from the motor or other prime mover into hydraulic energy. Its role is to provide pressure oil to the hydraulic system.

Working Principle of Hydraulic Pump

When the eccentric wheel rotates, the plunger is driven by the eccentric wheel and the action of the spring for left and right movement respectively.

When the plunger moves to the right, the sealing volume between its left end and the pump body increases, forming a local vacuum, and the oil in the tank enters the pump body through the check valve under atmospheric pressure, and the check valve seals the outlet to prevent the oil in the system from flowing back, at which time the hydraulic pump completes the oil suction process.

When the plunger moves to the left, the seal volume is reduced, the check valve seals the suction port to prevent the flow of oil back into the tank, so the oil in the pump body is squeezed, it will enter the system by the check valve, this time the hydraulic pump into the pressure process. If the eccentric wheel keeps rotating, the pump body is constantly sucking oil and pressure oil.

From the above, it can be seen that the hydraulic pump is through the change of the seal volume to the suction and pressure of oil. The use of this principle made of pressure pump is called displacement pump.

Features of Hydraulic Pumps

Single piston hydraulic pump has all the basic characteristics of the displacement hydraulic pump.

1. with a number of sealed and can also be periodically changing space. Hydraulic pump output flow and the volume of this space changes and the number of changes per unit of time is proportional to other factors. This is an important characteristic of the 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 conditions of the positive displacement hydraulic pump can suck the oil. Therefore, in order to ensure the normal suction of hydraulic pump, the tank must be connected to the atmosphere, or the use of closed pressure-filled tank.
3. With the corresponding flow distribution mechanism, the suction and discharge cavities are separated to ensure that the hydraulic pump regularly and continuously sucks and discharges liquid. Hydraulic pump structure principle is different, its oil distribution mechanism is also different.

Hydraulic pumps are divided into two categories: quantitative pumps and variable pumps according to whether the volume of oil output can be adjusted within a unit of time; and three categories: gear pumps, vane pumps and piston pumps according to the structure.

Main Performance Parameters of Hydraulic Pump

Pressure

1. Working pressure. The actual working output pressure of the hydraulic pump is called working pressure. The size of the working pressure depends on the size of the external load and the pressure loss on the discharge line, and has nothing to do with the flow of the hydraulic pump.
2. Rated pressure. Hydraulic pump in normal operating conditions, according to the test standard for continuous operation of the highest pressure is called the rated pressure of the hydraulic pump.
3. Maximum allowable pressure. In excess of the rated pressure conditions, according to the test standard, the highest pressure value of the hydraulic pump allowed to run briefly, known as the maximum allowable pressure of the hydraulic pump.

Displacement and Flow Rate

1.Displacement V. Hydraulic pump for each revolution, the volume of liquid discharged from its seal volume geometry change is called the displacement of the hydraulic pump. Displacement adjustable hydraulic pump is called variable pump; displacement of a constant hydraulic pump is called a quantitative pump.

2. theoretical flow qi. theoretical flow is the average value of the volume of liquid discharged in a unit of time without considering the leakage flow of the hydraulic pump. Obviously, if the displacement of the hydraulic pump for V, its spindle speed is n, then the hydraulic pump theoretical flow qi: qi = Vn (3-1)
3. the actual flow q. hydraulic pump in a specific condition, the unit of time the volume of liquid discharged is called the actual flow, which is equal to the theoretical flow qi minus the leakage flow Δq, that is: q = q = Δq (3-2)
4. rated flow qn. hydraulic pump under normal operating conditions, according to the test standard (such as in the rated pressure and rated speed) must ensure the flow rate.