Oil Trapping Noise and Noise Reduction Strategy of Hydraulic Gear Oil Pump
When the gear oil pump is working, part of the hydraulic oil is trapped in the closed volume formed by the meshing of two pairs of gears, which is not connected with the oil suction and pressure cavities.
The following are the noise generated by the trapped oil of the gear oil pump and the noise reduction methods:
1. Causes of noise:
When the gear oil pump is working, part of the hydraulic oil is trapped in the closed volume formed by the meshing of two pairs of gears, which is not connected with the oil suction and pressure cavities. When its capacity changes from large to small, the trapped hydraulic oil is squeezed, and the pressure speed rises, which is far higher than the output pressure of the gear oil pump (trapped liquid is forced out from the leaky gap), so that the shaft and the shaft bear considerable impact load, causing vibration and noise; When the trapped oil volume changes from small to large, a local vacuum is formed to separate the gas dissolved in the oil, resulting in "cavitation", cavitation, vibration and noise.
2. Noise reduction strategy:
1. The external meshing hydraulic gear oil pump is mainly used to open "unloading grooves" on internal components such as shaft sleeve (or inverted plate). The principle of slotting is to make sure that the high and low pressure chambers inside the gear oil pump do not communicate with each other, so that the trapped oil volume can be connected with the high pressure chamber or the low pressure chamber, so as to partially remove the trapped oil phenomenon, thereby reducing noise and vibration.
2. Increase the volume efficiency of the gear oil pump, reduce the internal leakage of the gear oil pump, so as to reduce the flow and pressure pulsation of the pump, and achieve the purpose of reducing noise. That is, the pump is equipped with an integral 8-shaped shaft sleeve with high accuracy, and the axial automatic compensation structure is used to reduce the leakage in the end face and increase the volume efficiency of the pump. At the same time, the layout of the "riveting groove" of the shaft sleeve is improved, and the asymmetric unloading groove is used to reduce the noise caused by trapped oil.
3. The internal gear structure of conjugate curve is used to reduce oil trapping. For example, the external gear profile of an internal gear oil pump uses straight lines, while the internal gear profile is the conjugate line of straight lines. The geometric shape of this pair of gear profiles determines that the trapped oil volume changes little. At the same time, because the pressure oil is led out from the bottom hole between the internal gear teeth, there is basically no trapped oil area during operation, so the gear pair transmission is quite stable without impact, and the pump flow and pressure pulsation are very small, In addition, the inlet area of the oil suction chamber is large and the oil suction is sufficient, which will not cause cavitation. Therefore, the noise of this pump is very low, which can be reduced to 55~65dB, and the application prospect is good.