Shenzhen Changheng Hydraulic Equipment Co., Ltd
Analysis of the causes of trapped oil noise and noise reduction strategies in hydraulic gear oil pumps by gear pump manufacturers
Analysis of the causes of trapped oil noise and noise reduction strategies in hydraulic gear oil pumps by gear pump manufacturers
In recent years, noise reduction has become an important technical indicator of hydraulic gear oil pumps. However, because the flow rate and pressure pulsation of gear oil pumps are their inherent characteristics, the causes of noise generation are relatively complex. It is often difficult to discover the reasons for noise generation only through theoretical analysis. Different methods and measures must be taken for different situations where noise is generated in order to effectively reduce noise
The following is an analysis of the noise generated by trapped oil in hydraulic gear oil pumps and the methods for noise reduction:
1、 The reasons for the noise generated by gear pumps:
During the operation of the gear oil pump, a portion of the hydraulic oil is trapped in a closed volume formed by the meshing of two pairs of gears, which is not connected to the suction and pressure oil chambers. When its capacity decreases from large to small, the trapped hydraulic oil is squeezed, and the pressure speed increases, far exceeding the output pressure of the gear oil pump (the trapped liquid is forcibly squeezed out from the leaky gap), causing the shaft to bear a considerable impact load, resulting in vibration and noise; When the trapped oil volume increases from small to large, a local vacuum is formed, which separates the dissolved gases in the oil and creates a "cavitation" phenomenon, causing cavitation, vibration, and noise.
2、 Methods to reduce gear pump noise:
1. Using a conjugate curve internal meshing gear structure to reduce oil entrapment. 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 the straight line. The geometric shape of this pair of gear profiles determines that the trapped oil volume changes less. At the same time, because the pressure oil is led out from the bottom hole between the teeth of the internal gear, there is basically no trapped oil area during operation, so the gear pair transmission is quite smooth and impact free. The flow rate and pressure pulsation of the pump are very small. In addition, the inlet area of the oil suction chamber is large, the oil suction is sufficient, and it will not cause cavitation phenomenon. Therefore, the noise of this pump is very low, which can be reduced to 55-65dB, and the application prospect is good.
2. The external meshing hydraulic gear oil pump mainly opens "unloading grooves" on internal components such as shaft sleeves (or reverse plates). The principle of slotting is to ensure that the high and low pressure chambers inside the gear oil pump do not communicate with each other, and to try to make the trapped oil volume communicate with the high or low pressure chamber, in order to partially remove the trapped oil phenomenon and reduce noise and vibration.
3. To increase the volumetric efficiency of the gear oil pump, reduce the internal leakage of the gear oil pump, thereby reducing the flow rate and pressure pulsation of the pump, and achieve the goal of reducing noise, a high-precision integral 8-shaped shaft sleeve is selected inside the pump, and an axial automatic compensation structure is used to reduce the leakage inside the end face and increase the volumetric efficiency of the pump. At the same time, improve the arrangement of the "rivet groove" on the shaft sleeve and adopt asymmetric relief grooves to reduce noise caused by trapped oil.
In recent years, noise reduction has become an important technical indicator of hydraulic gear oil pumps. However, because the flow rate and pressure pulsation of gear oil pumps are their inherent characteristics, the causes of noise generation are relatively complex. It is often difficult to discover the reasons for noise generation only through theoretical analysis. Different methods and measures must be taken for different situations where noise is generated in order to effectively reduce noise
The following is an analysis of the noise generated by trapped oil in hydraulic gear oil pumps and the methods for noise reduction:
1、 The reasons for the noise generated by gear pumps:
During the operation of the gear oil pump, a portion of the hydraulic oil is trapped in a closed volume formed by the meshing of two pairs of gears, which is not connected to the suction and pressure oil chambers. When its capacity decreases from large to small, the trapped hydraulic oil is squeezed, and the pressure speed increases, far exceeding the output pressure of the gear oil pump (the trapped liquid is forcibly squeezed out from the leaky gap), causing the shaft to bear a considerable impact load, resulting in vibration and noise; When the trapped oil volume increases from small to large, a local vacuum is formed, which separates the dissolved gases in the oil and creates a "cavitation" phenomenon, causing cavitation, vibration, and noise.
2、 Methods to reduce gear pump noise:
1. Using a conjugate curve internal meshing gear structure to reduce oil entrapment. 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 the straight line. The geometric shape of this pair of gear profiles determines that the trapped oil volume changes less. At the same time, because the pressure oil is led out from the bottom hole between the teeth of the internal gear, there is basically no trapped oil area during operation, so the gear pair transmission is quite smooth and impact free. The flow rate and pressure pulsation of the pump are very small. In addition, the inlet area of the oil suction chamber is large, the oil suction is sufficient, and it will not cause cavitation phenomenon. Therefore, the noise of this pump is very low, which can be reduced to 55-65dB, and the application prospect is good.
2. The external meshing hydraulic gear oil pump mainly opens "unloading grooves" on internal components such as shaft sleeves (or reverse plates). The principle of slotting is to ensure that the high and low pressure chambers inside the gear oil pump do not communicate with each other, and to try to make the trapped oil volume communicate with the high or low pressure chamber, in order to partially remove the trapped oil phenomenon and reduce noise and vibration.
3. To increase the volumetric efficiency of the gear oil pump, reduce the internal leakage of the gear oil pump, thereby reducing the flow rate and pressure pulsation of the pump, and achieve the goal of reducing noise, a high-precision integral 8-shaped shaft sleeve is selected inside the pump, and an axial automatic compensation structure is used to reduce the leakage inside the end face and increase the volumetric efficiency of the pump. At the same time, improve the arrangement of the "rivet groove" on the shaft sleeve and adopt asymmetric relief grooves to reduce noise caused by trapped oil.
