How much do you know about the loss of hydraulic oil pumps?

There are two types of losses when the hydraulic pump is working: one is mechanical loss, and the other is volume loss. So what causes it? The following editor will summarize and analyze with you:

(1) The main reason for the mechanical loss of the hydraulic pump

① When the hydraulic pump is working, there is mechanical friction between the relative moving parts, such as between the bearing and the shaft, between the shaft and the seal, between the blade and the inner wall of the pump, resulting in loss of frictional resistance. This loss is related to the output pressure of the hydraulic pump, the higher the output pressure, the greater the loss of frictional resistance.

② When the oil pressure flows in the oil pump, viscous resistance will be generated due to the viscosity of the liquid, which will also cause mechanical loss. This loss is related to the age of the oil and the speed of the pump. The more viscous the oil and the higher the speed of the pump, the greater the mechanical loss.

For the reasons stated above, the actual input power used is greater than the theoretically required power. The ratio of the theoretical input power of the oil pump to the actual input power is called mechanical efficiency, which indicates the degree of power loss. The ratio of the output rate of a hydraulic pump to the input power is called the overall efficiency of the hydraulic pump.

(2) Main causes of volume loss of hydraulic pumps

① Although the oil suction chamber and the oil discharge chamber of the positive displacement hydraulic pump are separated in the pump, there is always a certain gap between the relative movements. Therefore, the oil in the high-pressure area of the pump must leak to the low-pressure area through the gap. The lower the viscosity of the hydraulic oil, the greater the leakage at higher pressures.

② During the oil suction process of the hydraulic oil pump, due to reasons such as too much oil suction resistance, too viscous oil, or too high pump shaft speed, etc., it will cause the pump to suck empty, so that the sealed working volume cannot be filled with oil, that is to say, the hydraulic pump The working chamber is not fully utilized.

Due to the above reasons, the hydraulic pump has a volume loss. However, as long as the pump is designed correctly and used reasonably, the loss caused by the second reason can be overcome, which can reduce the volume loss of the pump. However, the volume loss caused by leakage when a hydraulic pump (including vane pump, piston pump, gear pump) is working is inevitable, that is, the volume loss of the pump can be approximately regarded as entirely caused by leakage, making the hydraulic pump The actual flow is always less than the theoretical flow. The ratio of the actual flow to the theoretical flow is called the volumetric efficiency, which indicates the degree of volume loss of the hydraulic pump. The volumetric efficiency of a hydraulic pump indicates the magnitude of the volume loss of the hydraulic pump.