In recent years, silence has been an important technical indicator of hydraulic gear oil pumps. However, because the flow rate and pressure pulsation of gear oil pumps are inherent characteristics, the causes of noise are more complicated, and it is often difficult to find noise generation only from theoretical analysis. The reason for this is that different methods and measures must be taken in accordance with the different situations in which the noise is generated, in order to effectively reduce the noise.

The following are the noise and noise reduction methods caused by the trapped oil of the gear oil pump:

1. Reasons for 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 and the suction and pressure oil chambers are not connected. When its capacity changes from large to small, the trapped hydraulic oil is squeezed, and the pressure speed increases, which is much higher than the output pressure of the gear oil pump (the trapped liquid is forced out of the leakable gap) , The shaft and bearing are subject to considerable impact load, causing vibration and noise; and when the trapped oil volume increases from small to large, a partial vacuum is formed to separate the gas dissolved in the oil, resulting in "cavitation". Bring cavitation, vibration and noise.

2. Noise reduction strategy:

1. The external meshing hydraulic gear oil pump is mainly to open "unloading grooves" on internal parts such as shaft sleeves (or inverted plates). The principle of grooving is to try to make the trapped oil volume communicate with the high pressure chamber or the low pressure chamber under the premise that the high and low pressure chambers inside the gear oil pump do not communicate with each other, so as to partially remove the trapped oil phenomenon, thereby reducing noise and vibration.

2. Increase the volumetric efficiency of the gear oil pump and reduce the internal leakage of the gear oil pump, thereby reducing the flow and pressure pulsation of the pump, and achieving the purpose of reducing noise. That is, the integral figure 8 bushing with higher accuracy is selected inside the pump and the shaft is used. The automatic compensation structure reduces the leakage in the end face and increases the volumetric efficiency of the pump. At the same time, the arrangement of the shaft sleeve "rivet load groove" is improved, and asymmetrical load relief groove is adopted to reduce the noise caused by trapped oil.

3. The internal meshing gear structure with conjugate curve is used to reduce oil trapping. For example, the external gear profile of a certain internal meshing hydraulic gear oil pump uses a straight line, while the internal gear profile is a conjugate line of straight money. The geometric shape of this pair of teeth profile determines the small change in the trapped oil volume. It is led out from the bottom hole between the teeth of the internal gear, and there is basically no oil trapped area when working, so the gear pair transmission is quite smooth and without impact, the flow and pressure pulsation of the pump are very small, and the inlet area of ​​the oil suction chamber is large, and the oil is sucked. It is sufficient and 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.