How to reduce noise during the production of rotary vane vacuum pump

The noise of the rotary vane vacuum pump usually refers to the noise level measured under the ultimate vacuum when the pump is stable in temperature.

It includes the noise of the pump itself and the noise of the motor. For the user, it also cares about the noise of the starting stage when the pump temperature is not stable, the noise of operation at different inlet pressures, and the noise of the open gas ballast. therefore. There are multiple factors to consider.

According to the location of the sound, the noise of the pump has the following possible aspects:

1. The impact of the rotary vane on the cylinder, the sound of the pressure oil in the residual volume of the pump and the exhaust dead space;

2. Impact of exhaust valve disc on valve seat and support;

3. Echoes and bubble bursts in the cabinet;

4. Bearing noise;

5. A lot of noise caused by gas and oil impacting the oil baffle;

6. Others. Such as transmission-induced noise, fan noise of air-cooled pumps, etc.

7. Motor noise, which is a crucial factor.

The design treatment proposal is described as follows:

1. The impact of the rotary blade on the cylinder wall.

If the design, manufacture or materials are not suitable, causing the rotor to slide poorly, or due to the existence of exhaust dead space, the incompressible oil causes the rotor head to not always run close to the cylinder wall, which will cause the rotor to move against the cylinder wall. Impact sounds. Therefore, a circular arc surface should be adopted to separate the inlet and exhaust ports. Eliminate dead spaces with exhaust deflectors. When using a line-separated structure, the distance from the exhaust end point to the tangent point should be shortened as much as possible. For rotary vane pumps below 70 l / s, considering the actual thickness of the rotary vane, it is recommended to take 7 ~ lomm, and a large pump with a large value. Too close, due to turning

The existence of the sub-rotary vane groove is in contact with only one narrow strip of the rotary vane head. Once the rotary vane is turned to the tangent point, the sealing effect will be poor, which will affect the pumping speed and even the ultimate pressure. It can be seen that this structure cannot completely eliminate the dead space of the exhaust gas, which limits the level of noise reduction.

It should be pointed out that excessive clearance between the rotor and the groove reduces performance. Therefore, it is necessary to ensure a reasonable tolerance fit and shape and position tolerance value, pay attention to the thermal expansion of the rotary blade, avoid burring of the rotary blade and the groove, pay attention to the cold oil viscosity of the oil, design sufficient rotary blade spring force, The additional eccentricity of the rotor center should not be too large. Otherwise, the rotating blade passes through the two circular arcs, which will cause a tendency to break away from the cylinder wall at the intersection point, instead causing an impact noise. Generally, the small pump is 0.20 ～ 0.25mm, and the large pump can be appropriately enlarged.

Sound of pressure oil in exhaust dead space and pressure oil in residual volume. When the pump reaches the extreme pressure, the two pressure oils will shoot into the vacuum chamber at high speed when they are connected with the vacuum chamber, and they will collide with the rotor and the cylinder wall to make sound.

The size and location of the two volumes are related to noise.

2.The impact noise of the valve plate on the valve seat and support

A large amount of gas is sucked in, and a large amount of oil is circulated by the pump, the noise of the valve plate becomes larger, the valve jumps, the valve area is large, the valve plate noise is also large, and the material of the valve plate is also affected. Noise from rubber valves should be better than steel or laminate. To this end, it is necessary to control the amount of oil input, and the valve discs must be closed in a timely manner and tightly. Pay attention to the material and structure of the valve.

3. This noise will increase when the volume of echo and bubble burst sound in the cabinet increases. Therefore, this noise will increase significantly when the gas ballast is turned on or when the atmosphere is vented. If the gas ballast is adjustable, the gas ballast can be reasonably adjusted.

4. Noise emitted when a large amount of gas and oil is discharged when it hits the oil baffle and other components. If the part is not rigid or is not fastened, vibration and collision will cause this noise to increase. Therefore, the oil baffle should not only have sufficient rigidity and tightening, but also, when it needs to contact with other parts (such as the fuel tank), the method of clamping rubber can be used to avoid collision noise caused by vibration and improve the oil blocking effect.